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tesseract/textord/imagefind.cpp
zdenop 9cf08ca8d3 fix build with -DGRAPHICS_DISABLED 
git-svn-id: https://tesseract-ocr.googlecode.com/svn/trunk@981 d0cd1f9f-072b-0410-8dd7-cf729c803f20
2014-01-11 23:08:54 +00:00

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///////////////////////////////////////////////////////////////////////
// File: imagefind.cpp
// Description: Function to find image and drawing regions in an image
// and create a corresponding list of empty blobs.
// Author: Ray Smith
// Created: Thu Mar 20 09:49:01 PDT 2008
//
// (C) Copyright 2008, Google Inc.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
///////////////////////////////////////////////////////////////////////
#ifdef _MSC_VER
#pragma warning(disable:4244) // Conversion warnings
#endif
#ifdef HAVE_CONFIG_H
#include "config_auto.h"
#endif
#include "imagefind.h"
#include "colpartitiongrid.h"
#include "linlsq.h"
#include "ndminx.h"
#include "statistc.h"
#include "params.h"
#include "allheaders.h"
INT_VAR(textord_tabfind_show_images, false, "Show image blobs");
namespace tesseract {
// Fraction of width or height of on pixels that can be discarded from a
// roughly rectangular image.
const double kMinRectangularFraction = 0.125;
// Fraction of width or height to consider image completely used.
const double kMaxRectangularFraction = 0.75;
// Fraction of width or height to allow transition from kMinRectangularFraction
// to kMaxRectangularFraction, equivalent to a dy/dx skew.
const double kMaxRectangularGradient = 0.1; // About 6 degrees.
// Minimum image size to be worth looking for images on.
const int kMinImageFindSize = 100;
// Scale factor for the rms color fit error.
const double kRMSFitScaling = 8.0;
// Min color difference to call it two colors.
const int kMinColorDifference = 16;
// Pixel padding for noise blobs and partitions when rendering on the image
// mask to encourage them to join together. Make it too big and images
// will fatten out too much and have to be clipped to text.
const int kNoisePadding = 4;
// Finds image regions within the BINARY source pix (page image) and returns
// the image regions as a mask image.
// The returned pix may be NULL, meaning no images found.
// If not NULL, it must be PixDestroyed by the caller.
Pix* ImageFind::FindImages(Pix* pix) {
// Not worth looking at small images.
if (pixGetWidth(pix) < kMinImageFindSize ||
pixGetHeight(pix) < kMinImageFindSize)
return pixCreate(pixGetWidth(pix), pixGetHeight(pix), 1);
// Reduce by factor 2.
Pix *pixr = pixReduceRankBinaryCascade(pix, 1, 0, 0, 0);
pixDisplayWrite(pixr, textord_tabfind_show_images);
// Get the halftone mask directly from Leptonica.
l_int32 ht_found = 0;
Pix *pixht2 = pixGenHalftoneMask(pixr, NULL, &ht_found,
textord_tabfind_show_images);
pixDestroy(&pixr);
if (!ht_found && pixht2 != NULL)
pixDestroy(&pixht2);
if (pixht2 == NULL)
return pixCreate(pixGetWidth(pix), pixGetHeight(pix), 1);
// Expand back up again.
Pix *pixht = pixExpandReplicate(pixht2, 2);
pixDisplayWrite(pixht, textord_tabfind_show_images);
pixDestroy(&pixht2);
// Fill to capture pixels near the mask edges that were missed
Pix *pixt = pixSeedfillBinary(NULL, pixht, pix, 8);
pixOr(pixht, pixht, pixt);
pixDestroy(&pixt);
// Eliminate lines and bars that may be joined to images.
Pix* pixfinemask = pixReduceRankBinaryCascade(pixht, 1, 1, 3, 3);
pixDilateBrick(pixfinemask, pixfinemask, 5, 5);
pixDisplayWrite(pixfinemask, textord_tabfind_show_images);
Pix* pixreduced = pixReduceRankBinaryCascade(pixht, 1, 1, 1, 1);
Pix* pixreduced2 = pixReduceRankBinaryCascade(pixreduced, 3, 3, 3, 0);
pixDestroy(&pixreduced);
pixDilateBrick(pixreduced2, pixreduced2, 5, 5);
Pix* pixcoarsemask = pixExpandReplicate(pixreduced2, 8);
pixDestroy(&pixreduced2);
pixDisplayWrite(pixcoarsemask, textord_tabfind_show_images);
// Combine the coarse and fine image masks.
pixAnd(pixcoarsemask, pixcoarsemask, pixfinemask);
pixDestroy(&pixfinemask);
// Dilate a bit to make sure we get everything.
pixDilateBrick(pixcoarsemask, pixcoarsemask, 3, 3);
Pix* pixmask = pixExpandReplicate(pixcoarsemask, 16);
pixDestroy(&pixcoarsemask);
if (textord_tabfind_show_images)
pixWrite("junkexpandedcoarsemask.png", pixmask, IFF_PNG);
// And the image mask with the line and bar remover.
pixAnd(pixht, pixht, pixmask);
pixDestroy(&pixmask);
if (textord_tabfind_show_images)
pixWrite("junkfinalimagemask.png", pixht, IFF_PNG);
// Make the result image the same size as the input.
Pix* result = pixCreate(pixGetWidth(pix), pixGetHeight(pix), 1);
pixOr(result, result, pixht);
pixDestroy(&pixht);
return result;
}
// Generates a Boxa, Pixa pair from the input binary (image mask) pix,
// analgous to pixConnComp, except that connected components which are nearly
// rectangular are replaced with solid rectangles.
// The returned boxa, pixa may be NULL, meaning no images found.
// If not NULL, they must be destroyed by the caller.
// Resolution of pix should match the source image (Tesseract::pix_binary_)
// so the output coordinate systems match.
void ImageFind::ConnCompAndRectangularize(Pix* pix, Boxa** boxa, Pixa** pixa) {
*boxa = NULL;
*pixa = NULL;
if (textord_tabfind_show_images)
pixWrite("junkconncompimage.png", pix, IFF_PNG);
// Find the individual image regions in the mask image.
*boxa = pixConnComp(pix, pixa, 8);
// Rectangularize the individual images. If a sharp edge in vertical and/or
// horizontal occupancy can be found, it indicates a probably rectangular
// image with unwanted bits merged on, so clip to the approximate rectangle.
int npixes = pixaGetCount(*pixa);
for (int i = 0; i < npixes; ++i) {
int x_start, x_end, y_start, y_end;
Pix* img_pix = pixaGetPix(*pixa, i, L_CLONE);
pixDisplayWrite(img_pix, textord_tabfind_show_images);
if (pixNearlyRectangular(img_pix, kMinRectangularFraction,
kMaxRectangularFraction,
kMaxRectangularGradient,
&x_start, &y_start, &x_end, &y_end)) {
Pix* simple_pix = pixCreate(x_end - x_start, y_end - y_start, 1);
pixSetAll(simple_pix);
pixDestroy(&img_pix);
// pixaReplacePix takes ownership of the simple_pix.
pixaReplacePix(*pixa, i, simple_pix, NULL);
img_pix = pixaGetPix(*pixa, i, L_CLONE);
// Fix the box to match the new pix.
l_int32 x, y, width, height;
boxaGetBoxGeometry(*boxa, i, &x, &y, &width, &height);
Box* simple_box = boxCreate(x + x_start, y + y_start,
x_end - x_start, y_end - y_start);
boxaReplaceBox(*boxa, i, simple_box);
}
pixDestroy(&img_pix);
}
}
// Scans horizontally on x=[x_start,x_end), starting with y=*y_start,
// stepping y+=y_step, until y=y_end. *ystart is input/output.
// If the number of black pixels in a row, pix_count fits this pattern:
// 0 or more rows with pix_count < min_count then
// <= mid_width rows with min_count <= pix_count <= max_count then
// a row with pix_count > max_count then
// true is returned, and *y_start = the first y with pix_count >= min_count.
static bool HScanForEdge(uinT32* data, int wpl, int x_start, int x_end,
int min_count, int mid_width, int max_count,
int y_end, int y_step, int* y_start) {
int mid_rows = 0;
for (int y = *y_start; y != y_end; y += y_step) {
// Need pixCountPixelsInRow(pix, y, &pix_count, NULL) to count in a subset.
int pix_count = 0;
uinT32* line = data + wpl * y;
for (int x = x_start; x < x_end; ++x) {
if (GET_DATA_BIT(line, x))
++pix_count;
}
if (mid_rows == 0 && pix_count < min_count)
continue; // In the min phase.
if (mid_rows == 0)
*y_start = y; // Save the y_start where we came out of the min phase.
if (pix_count > max_count)
return true; // Found the pattern.
++mid_rows;
if (mid_rows > mid_width)
break; // Middle too big.
}
return false; // Never found max_count.
}
// Scans vertically on y=[y_start,y_end), starting with x=*x_start,
// stepping x+=x_step, until x=x_end. *x_start is input/output.
// If the number of black pixels in a column, pix_count fits this pattern:
// 0 or more cols with pix_count < min_count then
// <= mid_width cols with min_count <= pix_count <= max_count then
// a column with pix_count > max_count then
// true is returned, and *x_start = the first x with pix_count >= min_count.
static bool VScanForEdge(uinT32* data, int wpl, int y_start, int y_end,
int min_count, int mid_width, int max_count,
int x_end, int x_step, int* x_start) {
int mid_cols = 0;
for (int x = *x_start; x != x_end; x += x_step) {
int pix_count = 0;
uinT32* line = data + y_start * wpl;
for (int y = y_start; y < y_end; ++y, line += wpl) {
if (GET_DATA_BIT(line, x))
++pix_count;
}
if (mid_cols == 0 && pix_count < min_count)
continue; // In the min phase.
if (mid_cols == 0)
*x_start = x; // Save the place where we came out of the min phase.
if (pix_count > max_count)
return true; // found the pattern.
++mid_cols;
if (mid_cols > mid_width)
break; // Middle too big.
}
return false; // Never found max_count.
}
// Returns true if there is a rectangle in the source pix, such that all
// pixel rows and column slices outside of it have less than
// min_fraction of the pixels black, and within max_skew_gradient fraction
// of the pixels on the inside, there are at least max_fraction of the
// pixels black. In other words, the inside of the rectangle looks roughly
// rectangular, and the outside of it looks like extra bits.
// On return, the rectangle is defined by x_start, y_start, x_end and y_end.
// Note: the algorithm is iterative, allowing it to slice off pixels from
// one edge, allowing it to then slice off more pixels from another edge.
bool ImageFind::pixNearlyRectangular(Pix* pix,
double min_fraction, double max_fraction,
double max_skew_gradient,
int* x_start, int* y_start,
int* x_end, int* y_end) {
ASSERT_HOST(pix != NULL);
*x_start = 0;
*x_end = pixGetWidth(pix);
*y_start = 0;
*y_end = pixGetHeight(pix);
uinT32* data = pixGetData(pix);
int wpl = pixGetWpl(pix);
bool any_cut = false;
bool left_done = false;
bool right_done = false;
bool top_done = false;
bool bottom_done = false;
do {
any_cut = false;
// Find the top/bottom edges.
int width = *x_end - *x_start;
int min_count = static_cast<int>(width * min_fraction);
int max_count = static_cast<int>(width * max_fraction);
int edge_width = static_cast<int>(width * max_skew_gradient);
if (HScanForEdge(data, wpl, *x_start, *x_end, min_count, edge_width,
max_count, *y_end, 1, y_start) && !top_done) {
top_done = true;
any_cut = true;
}
--(*y_end);
if (HScanForEdge(data, wpl, *x_start, *x_end, min_count, edge_width,
max_count, *y_start, -1, y_end) && !bottom_done) {
bottom_done = true;
any_cut = true;
}
++(*y_end);
// Find the left/right edges.
int height = *y_end - *y_start;
min_count = static_cast<int>(height * min_fraction);
max_count = static_cast<int>(height * max_fraction);
edge_width = static_cast<int>(height * max_skew_gradient);
if (VScanForEdge(data, wpl, *y_start, *y_end, min_count, edge_width,
max_count, *x_end, 1, x_start) && !left_done) {
left_done = true;
any_cut = true;
}
--(*x_end);
if (VScanForEdge(data, wpl, *y_start, *y_end, min_count, edge_width,
max_count, *x_start, -1, x_end) && !right_done) {
right_done = true;
any_cut = true;
}
++(*x_end);
} while (any_cut);
// All edges must satisfy the condition of sharp gradient in pixel density
// in order for the full rectangle to be present.
return left_done && right_done && top_done && bottom_done;
}
// Given an input pix, and a bounding rectangle, the sides of the rectangle
// are shrunk inwards until they bound any black pixels found within the
// original rectangle. Returns false if the rectangle contains no black
// pixels at all.
bool ImageFind::BoundsWithinRect(Pix* pix, int* x_start, int* y_start,
int* x_end, int* y_end) {
Box* input_box = boxCreate(*x_start, *y_start, *x_end - *x_start,
*y_end - *y_start);
Box* output_box = NULL;
pixClipBoxToForeground(pix, input_box, NULL, &output_box);
bool result = output_box != NULL;
if (result) {
l_int32 x, y, width, height;
boxGetGeometry(output_box, &x, &y, &width, &height);
*x_start = x;
*y_start = y;
*x_end = x + width;
*y_end = y + height;
boxDestroy(&output_box);
}
boxDestroy(&input_box);
return result;
}
// Given a point in 3-D (RGB) space, returns the squared Euclidean distance
// of the point from the given line, defined by a pair of points in the 3-D
// (RGB) space, line1 and line2.
double ImageFind::ColorDistanceFromLine(const uinT8* line1,
const uinT8* line2,
const uinT8* point) {
int line_vector[kRGBRMSColors];
int point_vector[kRGBRMSColors];
for (int i = 0; i < kRGBRMSColors; ++i) {
line_vector[i] = static_cast<int>(line2[i]) - static_cast<int>(line1[i]);
point_vector[i] = static_cast<int>(point[i]) - static_cast<int>(line1[i]);
}
line_vector[L_ALPHA_CHANNEL] = 0;
// Now the cross product in 3d.
int cross[kRGBRMSColors];
cross[COLOR_RED] = line_vector[COLOR_GREEN] * point_vector[COLOR_BLUE]
- line_vector[COLOR_BLUE] * point_vector[COLOR_GREEN];
cross[COLOR_GREEN] = line_vector[COLOR_BLUE] * point_vector[COLOR_RED]
- line_vector[COLOR_RED] * point_vector[COLOR_BLUE];
cross[COLOR_BLUE] = line_vector[COLOR_RED] * point_vector[COLOR_GREEN]
- line_vector[COLOR_GREEN] * point_vector[COLOR_RED];
cross[L_ALPHA_CHANNEL] = 0;
// Now the sums of the squares.
double cross_sq = 0.0;
double line_sq = 0.0;
for (int j = 0; j < kRGBRMSColors; ++j) {
cross_sq += static_cast<double>(cross[j]) * cross[j];
line_sq += static_cast<double>(line_vector[j]) * line_vector[j];
}
if (line_sq == 0.0) {
return 0.0;
}
return cross_sq / line_sq; // This is the squared distance.
}
// Returns the leptonica combined code for the given RGB triplet.
uinT32 ImageFind::ComposeRGB(uinT32 r, uinT32 g, uinT32 b) {
l_uint32 result;
composeRGBPixel(r, g, b, &result);
return result;
}
// Returns the input value clipped to a uinT8.
uinT8 ImageFind::ClipToByte(double pixel) {
if (pixel < 0.0)
return 0;
else if (pixel >= 255.0)
return 255;
return static_cast<uinT8>(pixel);
}
// Computes the light and dark extremes of color in the given rectangle of
// the given pix, which is factor smaller than the coordinate system in rect.
// The light and dark points are taken to be the upper and lower 8th-ile of
// the most deviant of R, G and B. The value of the other 2 channels are
// computed by linear fit against the most deviant.
// The colors of the two points are returned in color1 and color2, with the
// alpha channel set to a scaled mean rms of the fits.
// If color_map1 is not null then it and color_map2 get rect pasted in them
// with the two calculated colors, and rms map gets a pasted rect of the rms.
// color_map1, color_map2 and rms_map are assumed to be the same scale as pix.
void ImageFind::ComputeRectangleColors(const TBOX& rect, Pix* pix, int factor,
Pix* color_map1, Pix* color_map2,
Pix* rms_map,
uinT8* color1, uinT8* color2) {
ASSERT_HOST(pix != NULL && pixGetDepth(pix) == 32);
// Pad the rectangle outwards by 2 (scaled) pixels if possible to get more
// background.
int width = pixGetWidth(pix);
int height = pixGetHeight(pix);
int left_pad = MAX(rect.left() - 2 * factor, 0) / factor;
int top_pad = (rect.top() + 2 * factor + (factor - 1)) / factor;
top_pad = MIN(height, top_pad);
int right_pad = (rect.right() + 2 * factor + (factor - 1)) / factor;
right_pad = MIN(width, right_pad);
int bottom_pad = MAX(rect.bottom() - 2 * factor, 0) / factor;
int width_pad = right_pad - left_pad;
int height_pad = top_pad - bottom_pad;
if (width_pad < 1 || height_pad < 1 || width_pad + height_pad < 4)
return;
// Now crop the pix to the rectangle.
Box* scaled_box = boxCreate(left_pad, height - top_pad,
width_pad, height_pad);
Pix* scaled = pixClipRectangle(pix, scaled_box, NULL);
// Compute stats over the whole image.
STATS red_stats(0, 256);
STATS green_stats(0, 256);
STATS blue_stats(0, 256);
uinT32* data = pixGetData(scaled);
ASSERT_HOST(pixGetWpl(scaled) == width_pad);
for (int y = 0; y < height_pad; ++y) {
for (int x = 0; x < width_pad; ++x, ++data) {
int r = GET_DATA_BYTE(data, COLOR_RED);
int g = GET_DATA_BYTE(data, COLOR_GREEN);
int b = GET_DATA_BYTE(data, COLOR_BLUE);
red_stats.add(r, 1);
green_stats.add(g, 1);
blue_stats.add(b, 1);
}
}
// Find the RGB component with the greatest 8th-ile-range.
// 8th-iles are used instead of quartiles to get closer to the true
// foreground color, which is going to be faint at best because of the
// pre-scaling of the input image.
int best_l8 = static_cast<int>(red_stats.ile(0.125f));
int best_u8 = static_cast<int>(ceil(red_stats.ile(0.875f)));
int best_i8r = best_u8 - best_l8;
int x_color = COLOR_RED;
int y1_color = COLOR_GREEN;
int y2_color = COLOR_BLUE;
int l8 = static_cast<int>(green_stats.ile(0.125f));
int u8 = static_cast<int>(ceil(green_stats.ile(0.875f)));
if (u8 - l8 > best_i8r) {
best_i8r = u8 - l8;
best_l8 = l8;
best_u8 = u8;
x_color = COLOR_GREEN;
y1_color = COLOR_RED;
}
l8 = static_cast<int>(blue_stats.ile(0.125f));
u8 = static_cast<int>(ceil(blue_stats.ile(0.875f)));
if (u8 - l8 > best_i8r) {
best_i8r = u8 - l8;
best_l8 = l8;
best_u8 = u8;
x_color = COLOR_BLUE;
y1_color = COLOR_GREEN;
y2_color = COLOR_RED;
}
if (best_i8r >= kMinColorDifference) {
LLSQ line1;
LLSQ line2;
uinT32* data = pixGetData(scaled);
for (int im_y = 0; im_y < height_pad; ++im_y) {
for (int im_x = 0; im_x < width_pad; ++im_x, ++data) {
int x = GET_DATA_BYTE(data, x_color);
int y1 = GET_DATA_BYTE(data, y1_color);
int y2 = GET_DATA_BYTE(data, y2_color);
line1.add(x, y1);
line2.add(x, y2);
}
}
double m1 = line1.m();
double c1 = line1.c(m1);
double m2 = line2.m();
double c2 = line2.c(m2);
double rms = line1.rms(m1, c1) + line2.rms(m2, c2);
rms *= kRMSFitScaling;
// Save the results.
color1[x_color] = ClipToByte(best_l8);
color1[y1_color] = ClipToByte(m1 * best_l8 + c1 + 0.5);
color1[y2_color] = ClipToByte(m2 * best_l8 + c2 + 0.5);
color1[L_ALPHA_CHANNEL] = ClipToByte(rms);
color2[x_color] = ClipToByte(best_u8);
color2[y1_color] = ClipToByte(m1 * best_u8 + c1 + 0.5);
color2[y2_color] = ClipToByte(m2 * best_u8 + c2 + 0.5);
color2[L_ALPHA_CHANNEL] = ClipToByte(rms);
} else {
// There is only one color.
color1[COLOR_RED] = ClipToByte(red_stats.median());
color1[COLOR_GREEN] = ClipToByte(green_stats.median());
color1[COLOR_BLUE] = ClipToByte(blue_stats.median());
color1[L_ALPHA_CHANNEL] = 0;
memcpy(color2, color1, 4);
}
if (color_map1 != NULL) {
pixSetInRectArbitrary(color_map1, scaled_box,
ComposeRGB(color1[COLOR_RED],
color1[COLOR_GREEN],
color1[COLOR_BLUE]));
pixSetInRectArbitrary(color_map2, scaled_box,
ComposeRGB(color2[COLOR_RED],
color2[COLOR_GREEN],
color2[COLOR_BLUE]));
pixSetInRectArbitrary(rms_map, scaled_box, color1[L_ALPHA_CHANNEL]);
}
pixDestroy(&scaled);
boxDestroy(&scaled_box);
}
// ================ CUTTING POLYGONAL IMAGES FROM A RECTANGLE ================
// The following functions are responsible for cutting a polygonal image from
// a rectangle: CountPixelsInRotatedBox, AttemptToShrinkBox, CutChunkFromParts
// with DivideImageIntoParts as the master.
// Problem statement:
// We start with a single connected component from the image mask: we get
// a Pix of the component, and its location on the page (im_box).
// The objective of cutting a polygonal image from its rectangle is to avoid
// interfering text, but not text that completely overlaps the image.
// ------------------------------ ------------------------------
// | Single input partition | | 1 Cut up output partitions |
// | | ------------------------------
// Av|oid | Avoid | |
// | | |________________________|
// Int|erfering | Interfering | |
// | | _____|__________________|
// T|ext | Text | |
// | Text-on-image | | Text-on-image |
// ------------------------------ --------------------------
// DivideImageIntoParts does this by building a ColPartition_LIST (not in the
// grid) with each ColPartition representing one of the rectangles needed,
// starting with a single rectangle for the whole image component, and cutting
// bits out of it with CutChunkFromParts as needed to avoid text. The output
// ColPartitions are supposed to be ordered from top to bottom.
// The problem is complicated by the fact that we have rotated the coordinate
// system to make text lines horizontal, so if we need to look at the component
// image, we have to rotate the coordinates. Throughout the functions in this
// section im_box is the rectangle representing the image component in the
// rotated page coordinates (where we are building our output ColPartitions),
// rotation is the rotation that we used to get there, and rerotation is the
// rotation required to get back to original page image coordinates.
// To get to coordinates in the component image, pix, we rotate the im_box,
// the point we want to locate, and subtract the rotated point from the top-left
// of the rotated im_box.
// im_box is therefore essential to calculating coordinates within the pix.
// Returns true if there are no black pixels in between the boxes.
// The im_box must represent the bounding box of the pix in tesseract
// coordinates, which may be negative, due to rotations to make the textlines
// horizontal. The boxes are rotated by rotation, which should undo such
// rotations, before mapping them onto the pix.
bool ImageFind::BlankImageInBetween(const TBOX& box1, const TBOX& box2,
const TBOX& im_box, const FCOORD& rotation,
Pix* pix) {
TBOX search_box(box1);
search_box += box2;
if (box1.x_gap(box2) >= box1.y_gap(box2)) {
if (box1.x_gap(box2) <= 0)
return true;
search_box.set_left(MIN(box1.right(), box2.right()));
search_box.set_right(MAX(box1.left(), box2.left()));
} else {
if (box1.y_gap(box2) <= 0)
return true;
search_box.set_top(MAX(box1.bottom(), box2.bottom()));
search_box.set_bottom(MIN(box1.top(), box2.top()));
}
return CountPixelsInRotatedBox(search_box, im_box, rotation, pix) == 0;
}
// Returns the number of pixels in box in the pix.
// rotation, pix and im_box are defined in the large comment above.
int ImageFind::CountPixelsInRotatedBox(TBOX box, const TBOX& im_box,
const FCOORD& rotation, Pix* pix) {
// Intersect it with the image box.
box &= im_box; // This is in-place box intersection.
if (box.null_box())
return 0;
box.rotate(rotation);
TBOX rotated_im_box(im_box);
rotated_im_box.rotate(rotation);
Pix* rect_pix = pixCreate(box.width(), box.height(), 1);
pixRasterop(rect_pix, 0, 0, box.width(), box.height(),
PIX_SRC, pix, box.left() - rotated_im_box.left(),
rotated_im_box.top() - box.top());
l_int32 result;
pixCountPixels(rect_pix, &result, NULL);
pixDestroy(&rect_pix);
return result;
}
// The box given by slice contains some black pixels, but not necessarily
// over the whole box. Shrink the x bounds of slice, but not the y bounds
// until there is at least one black pixel in the outermost columns.
// rotation, rerotation, pix and im_box are defined in the large comment above.
static void AttemptToShrinkBox(const FCOORD& rotation, const FCOORD& rerotation,
const TBOX& im_box, Pix* pix, TBOX* slice) {
TBOX rotated_box(*slice);
rotated_box.rotate(rerotation);
TBOX rotated_im_box(im_box);
rotated_im_box.rotate(rerotation);
int left = rotated_box.left() - rotated_im_box.left();
int right = rotated_box.right() - rotated_im_box.left();
int top = rotated_im_box.top() - rotated_box.top();
int bottom = rotated_im_box.top() - rotated_box.bottom();
ImageFind::BoundsWithinRect(pix, &left, &top, &right, &bottom);
top = rotated_im_box.top() - top;
bottom = rotated_im_box.top() - bottom;
left += rotated_im_box.left();
right += rotated_im_box.left();
rotated_box.set_to_given_coords(left, bottom, right, top);
rotated_box.rotate(rotation);
slice->set_left(rotated_box.left());
slice->set_right(rotated_box.right());
}
// The meat of cutting a polygonal image around text.
// This function covers the general case of cutting a box out of a box
// as shown:
// Input Output
// ------------------------------ ------------------------------
// | Single input partition | | 1 Cut up output partitions |
// | | ------------------------------
// | ---------- | --------- ----------
// | | box | | | 2 | box | 3 |
// | | | | | | is cut | |
// | ---------- | --------- out ----------
// | | ------------------------------
// | | | 4 |
// ------------------------------ ------------------------------
// In the context that this function is used, at most 3 of the above output
// boxes will be created, as the overlapping box is never contained by the
// input.
// The above cutting operation is executed for each element of part_list that
// is overlapped by the input box. Each modified ColPartition is replaced
// in place in the list by the output of the cutting operation in the order
// shown above, so iff no holes are ever created, the output will be in
// top-to-bottom order, but in extreme cases, hole creation is possible.
// In such cases, the output order may cause strange block polygons.
// rotation, rerotation, pix and im_box are defined in the large comment above.
static void CutChunkFromParts(const TBOX& box, const TBOX& im_box,
const FCOORD& rotation, const FCOORD& rerotation,
Pix* pix, ColPartition_LIST* part_list) {
ASSERT_HOST(!part_list->empty());
ColPartition_IT part_it(part_list);
do {
ColPartition* part = part_it.data();
TBOX part_box = part->bounding_box();
if (part_box.overlap(box)) {
// This part must be cut and replaced with the remains. There are
// upto 4 pieces to be made. Start with the first one and use
// add_before_stay_put. For each piece if it has no black pixels
// left, just don't make the box.
// Above box.
if (box.top() < part_box.top()) {
TBOX slice(part_box);
slice.set_bottom(box.top());
if (ImageFind::CountPixelsInRotatedBox(slice, im_box, rerotation,
pix) > 0) {
AttemptToShrinkBox(rotation, rerotation, im_box, pix, &slice);
part_it.add_before_stay_put(
ColPartition::FakePartition(slice, PT_UNKNOWN, BRT_POLYIMAGE,
BTFT_NONTEXT));
}
}
// Left of box.
if (box.left() > part_box.left()) {
TBOX slice(part_box);
slice.set_right(box.left());
if (box.top() < part_box.top())
slice.set_top(box.top());
if (box.bottom() > part_box.bottom())
slice.set_bottom(box.bottom());
if (ImageFind::CountPixelsInRotatedBox(slice, im_box, rerotation,
pix) > 0) {
AttemptToShrinkBox(rotation, rerotation, im_box, pix, &slice);
part_it.add_before_stay_put(
ColPartition::FakePartition(slice, PT_UNKNOWN, BRT_POLYIMAGE,
BTFT_NONTEXT));
}
}
// Right of box.
if (box.right() < part_box.right()) {
TBOX slice(part_box);
slice.set_left(box.right());
if (box.top() < part_box.top())
slice.set_top(box.top());
if (box.bottom() > part_box.bottom())
slice.set_bottom(box.bottom());
if (ImageFind::CountPixelsInRotatedBox(slice, im_box, rerotation,
pix) > 0) {
AttemptToShrinkBox(rotation, rerotation, im_box, pix, &slice);
part_it.add_before_stay_put(
ColPartition::FakePartition(slice, PT_UNKNOWN, BRT_POLYIMAGE,
BTFT_NONTEXT));
}
}
// Below box.
if (box.bottom() > part_box.bottom()) {
TBOX slice(part_box);
slice.set_top(box.bottom());
if (ImageFind::CountPixelsInRotatedBox(slice, im_box, rerotation,
pix) > 0) {
AttemptToShrinkBox(rotation, rerotation, im_box, pix, &slice);
part_it.add_before_stay_put(
ColPartition::FakePartition(slice, PT_UNKNOWN, BRT_POLYIMAGE,
BTFT_NONTEXT));
}
}
part->DeleteBoxes();
delete part_it.extract();
}
part_it.forward();
} while (!part_it.at_first());
}
// Starts with the bounding box of the image component and cuts it up
// so that it doesn't intersect text where possible.
// Strong fully contained horizontal text is marked as text on image,
// and does not cause a division of the image.
// For more detail see the large comment above on cutting polygonal images
// from a rectangle.
// rotation, rerotation, pix and im_box are defined in the large comment above.
static void DivideImageIntoParts(const TBOX& im_box, const FCOORD& rotation,
const FCOORD& rerotation, Pix* pix,
ColPartitionGridSearch* rectsearch,
ColPartition_LIST* part_list) {
// Add the full im_box partition to the list to begin with.
ColPartition* pix_part = ColPartition::FakePartition(im_box, PT_UNKNOWN,
BRT_RECTIMAGE,
BTFT_NONTEXT);
ColPartition_IT part_it(part_list);
part_it.add_after_then_move(pix_part);
rectsearch->StartRectSearch(im_box);
ColPartition* part;
while ((part = rectsearch->NextRectSearch()) != NULL) {
TBOX part_box = part->bounding_box();
if (part_box.contains(im_box) && part->flow() >= BTFT_CHAIN) {
// This image is completely covered by an existing text partition.
for (part_it.move_to_first(); !part_it.empty(); part_it.forward()) {
ColPartition* pix_part = part_it.extract();
pix_part->DeleteBoxes();
delete pix_part;
}
} else if (part->flow() == BTFT_STRONG_CHAIN) {
// Text intersects the box.
TBOX overlap_box = part_box.intersection(im_box);
// Intersect it with the image box.
int black_area = ImageFind::CountPixelsInRotatedBox(overlap_box, im_box,
rerotation, pix);
if (black_area * 2 < part_box.area() || !im_box.contains(part_box)) {
// Eat a piece out of the image.
// Pad it so that pieces eaten out look decent.
int padding = part->blob_type() == BRT_VERT_TEXT
? part_box.width() : part_box.height();
part_box.set_top(part_box.top() + padding / 2);
part_box.set_bottom(part_box.bottom() - padding / 2);
CutChunkFromParts(part_box, im_box, rotation, rerotation,
pix, part_list);
} else {
// Strong overlap with the black area, so call it text on image.
part->set_flow(BTFT_TEXT_ON_IMAGE);
}
}
if (part_list->empty()) {
break;
}
}
}
// Search for the rightmost text that overlaps vertically and is to the left
// of the given box, but within the given left limit.
static int ExpandImageLeft(const TBOX& box, int left_limit,
ColPartitionGrid* part_grid) {
ColPartitionGridSearch search(part_grid);
ColPartition* part;
// Search right to left for any text that overlaps.
search.StartSideSearch(box.left(), box.bottom(), box.top());
while ((part = search.NextSideSearch(true)) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.y_gap(box) < 0) {
if (part_box.right() > left_limit && part_box.right() < box.left())
left_limit = part_box.right();
break;
}
}
}
if (part != NULL) {
// Search for the nearest text up to the one we already found.
TBOX search_box(left_limit, box.bottom(), box.left(), box.top());
search.StartRectSearch(search_box);
while ((part = search.NextRectSearch()) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.y_gap(box) < 0) {
if (part_box.right() > left_limit && part_box.right() < box.left()) {
left_limit = part_box.right();
}
}
}
}
}
return left_limit;
}
// Search for the leftmost text that overlaps vertically and is to the right
// of the given box, but within the given right limit.
static int ExpandImageRight(const TBOX& box, int right_limit,
ColPartitionGrid* part_grid) {
ColPartitionGridSearch search(part_grid);
ColPartition* part;
// Search left to right for any text that overlaps.
search.StartSideSearch(box.right(), box.bottom(), box.top());
while ((part = search.NextSideSearch(false)) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.y_gap(box) < 0) {
if (part_box.left() < right_limit && part_box.left() > box.right())
right_limit = part_box.left();
break;
}
}
}
if (part != NULL) {
// Search for the nearest text up to the one we already found.
TBOX search_box(box.left(), box.bottom(), right_limit, box.top());
search.StartRectSearch(search_box);
while ((part = search.NextRectSearch()) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.y_gap(box) < 0) {
if (part_box.left() < right_limit && part_box.left() > box.right())
right_limit = part_box.left();
}
}
}
}
return right_limit;
}
// Search for the topmost text that overlaps horizontally and is below
// the given box, but within the given bottom limit.
static int ExpandImageBottom(const TBOX& box, int bottom_limit,
ColPartitionGrid* part_grid) {
ColPartitionGridSearch search(part_grid);
ColPartition* part;
// Search right to left for any text that overlaps.
search.StartVerticalSearch(box.left(), box.right(), box.bottom());
while ((part = search.NextVerticalSearch(true)) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.x_gap(box) < 0) {
if (part_box.top() > bottom_limit && part_box.top() < box.bottom())
bottom_limit = part_box.top();
break;
}
}
}
if (part != NULL) {
// Search for the nearest text up to the one we already found.
TBOX search_box(box.left(), bottom_limit, box.right(), box.bottom());
search.StartRectSearch(search_box);
while ((part = search.NextRectSearch()) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.x_gap(box) < 0) {
if (part_box.top() > bottom_limit && part_box.top() < box.bottom())
bottom_limit = part_box.top();
}
}
}
}
return bottom_limit;
}
// Search for the bottommost text that overlaps horizontally and is above
// the given box, but within the given top limit.
static int ExpandImageTop(const TBOX& box, int top_limit,
ColPartitionGrid* part_grid) {
ColPartitionGridSearch search(part_grid);
ColPartition* part;
// Search right to left for any text that overlaps.
search.StartVerticalSearch(box.left(), box.right(), box.top());
while ((part = search.NextVerticalSearch(false)) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.x_gap(box) < 0) {
if (part_box.bottom() < top_limit && part_box.bottom() > box.top())
top_limit = part_box.bottom();
break;
}
}
}
if (part != NULL) {
// Search for the nearest text up to the one we already found.
TBOX search_box(box.left(), box.top(), box.right(), top_limit);
search.StartRectSearch(search_box);
while ((part = search.NextRectSearch()) != NULL) {
if (part->flow() == BTFT_STRONG_CHAIN || part->flow() == BTFT_CHAIN) {
const TBOX& part_box(part->bounding_box());
if (part_box.x_gap(box) < 0) {
if (part_box.bottom() < top_limit && part_box.bottom() > box.top())
top_limit = part_box.bottom();
}
}
}
}
return top_limit;
}
// Expands the image box in the given direction until it hits text,
// limiting the expansion to the given limit box, returning the result
// in the expanded box, and
// returning the increase in area resulting from the expansion.
static int ExpandImageDir(BlobNeighbourDir dir, const TBOX& im_box,
const TBOX& limit_box,
ColPartitionGrid* part_grid, TBOX* expanded_box) {
*expanded_box = im_box;
switch (dir) {
case BND_LEFT:
expanded_box->set_left(ExpandImageLeft(im_box, limit_box.left(),
part_grid));
break;
case BND_RIGHT:
expanded_box->set_right(ExpandImageRight(im_box, limit_box.right(),
part_grid));
break;
case BND_ABOVE:
expanded_box->set_top(ExpandImageTop(im_box, limit_box.top(), part_grid));
break;
case BND_BELOW:
expanded_box->set_bottom(ExpandImageBottom(im_box, limit_box.bottom(),
part_grid));
break;
default:
return 0;
}
return expanded_box->area() - im_box.area();
}
// Expands the image partition into any non-text until it touches text.
// The expansion proceeds in the order of increasing increase in area
// as a heuristic to find the best rectangle by expanding in the most
// constrained direction first.
static void MaximalImageBoundingBox(ColPartitionGrid* part_grid, TBOX* im_box) {
bool dunnit[BND_COUNT];
memset(dunnit, 0, sizeof(dunnit));
TBOX limit_box(part_grid->bleft().x(), part_grid->bleft().y(),
part_grid->tright().x(), part_grid->tright().y());
TBOX text_box(*im_box);
for (int iteration = 0; iteration < BND_COUNT; ++iteration) {
// Find the direction with least area increase.
int best_delta = -1;
BlobNeighbourDir best_dir = BND_LEFT;
TBOX expanded_boxes[BND_COUNT];
for (int dir = 0; dir < BND_COUNT; ++dir) {
BlobNeighbourDir bnd = static_cast<BlobNeighbourDir>(dir);
if (!dunnit[bnd]) {
TBOX expanded_box;
int area_delta = ExpandImageDir(bnd, text_box, limit_box, part_grid,
&expanded_boxes[bnd]);
if (best_delta < 0 || area_delta < best_delta) {
best_delta = area_delta;
best_dir = bnd;
}
}
}
// Run the best and remember the direction.
dunnit[best_dir] = true;
text_box = expanded_boxes[best_dir];
}
*im_box = text_box;
}
// Helper deletes the given partition but first marks up all the blobs as
// noise, so they get deleted later, and disowns them.
// If the initial type of the partition is image, then it actually deletes
// the blobs, as the partition owns them in that case.
static void DeletePartition(ColPartition* part) {
BlobRegionType type = part->blob_type();
if (type == BRT_RECTIMAGE || type == BRT_POLYIMAGE) {
// The partition owns the boxes of these types, so just delete them.
part->DeleteBoxes(); // From a previous iteration.
} else {
// Once marked, the blobs will be swept up by TidyBlobs.
part->set_flow(BTFT_NONTEXT);
part->set_blob_type(BRT_NOISE);
part->SetBlobTypes();
part->DisownBoxes(); // Created before FindImagePartitions.
}
delete part;
}
// The meat of joining fragmented images and consuming ColPartitions of
// uncertain type.
// *part_ptr is an input/output BRT_RECTIMAGE ColPartition that is to be
// expanded to consume overlapping and nearby ColPartitions of uncertain type
// and other BRT_RECTIMAGE partitions, but NOT to be expanded beyond
// max_image_box. *part_ptr is NOT in the part_grid.
// rectsearch is already constructed on the part_grid, and is used for
// searching for overlapping and nearby ColPartitions.
// ExpandImageIntoParts is called iteratively until it returns false. Each
// time it absorbs the nearest non-contained candidate, and everything that
// is fully contained within part_ptr's bounding box.
// TODO(rays) what if it just eats everything inside max_image_box in one go?
static bool ExpandImageIntoParts(const TBOX& max_image_box,
ColPartitionGridSearch* rectsearch,
ColPartitionGrid* part_grid,
ColPartition** part_ptr) {
ColPartition* image_part = *part_ptr;
TBOX im_part_box = image_part->bounding_box();
if (textord_tabfind_show_images > 1) {
tprintf("Searching for merge with image part:");
im_part_box.print();
tprintf("Text box=");
max_image_box.print();
}
rectsearch->StartRectSearch(max_image_box);
ColPartition* part;
ColPartition* best_part = NULL;
int best_dist = 0;
while ((part = rectsearch->NextRectSearch()) != NULL) {
if (textord_tabfind_show_images > 1) {
tprintf("Considering merge with part:");
part->Print();
if (im_part_box.contains(part->bounding_box()))
tprintf("Fully contained\n");
else if (!max_image_box.contains(part->bounding_box()))
tprintf("Not within text box\n");
else if (part->flow() == BTFT_STRONG_CHAIN)
tprintf("Too strong text\n");
else
tprintf("Real candidate\n");
}
if (part->flow() == BTFT_STRONG_CHAIN ||
part->flow() == BTFT_TEXT_ON_IMAGE ||
part->blob_type() == BRT_POLYIMAGE)
continue;
TBOX box = part->bounding_box();
if (max_image_box.contains(box) && part->blob_type() != BRT_NOISE) {
if (im_part_box.contains(box)) {
// Eat it completely.
rectsearch->RemoveBBox();
DeletePartition(part);
continue;
}
int x_dist = MAX(0, box.x_gap(im_part_box));
int y_dist = MAX(0, box.y_gap(im_part_box));
int dist = x_dist * x_dist + y_dist * y_dist;
if (dist > box.area() || dist > im_part_box.area())
continue; // Not close enough.
if (best_part == NULL || dist < best_dist) {
// We keep the nearest qualifier, which is not necessarily the nearest.
best_part = part;
best_dist = dist;
}
}
}
if (best_part != NULL) {
// It needs expanding. We can do it without touching text.
TBOX box = best_part->bounding_box();
if (textord_tabfind_show_images > 1) {
tprintf("Merging image part:");
im_part_box.print();
tprintf("with part:");
box.print();
}
im_part_box += box;
*part_ptr = ColPartition::FakePartition(im_part_box, PT_UNKNOWN,
BRT_RECTIMAGE,
BTFT_NONTEXT);
DeletePartition(image_part);
part_grid->RemoveBBox(best_part);
DeletePartition(best_part);
rectsearch->RepositionIterator();
return true;
}
return false;
}
// Helper function to compute the overlap area between the box and the
// given list of partitions.
static int IntersectArea(const TBOX& box, ColPartition_LIST* part_list) {
int intersect_area = 0;
ColPartition_IT part_it(part_list);
// Iterate the parts and subtract intersecting area.
for (part_it.mark_cycle_pt(); !part_it.cycled_list();
part_it.forward()) {
ColPartition* image_part = part_it.data();
TBOX intersect = box.intersection(image_part->bounding_box());
intersect_area += intersect.area();
}
return intersect_area;
}
// part_list is a set of ColPartitions representing a polygonal image, and
// im_box is the union of the bounding boxes of all the parts in part_list.
// Tests whether part is to be consumed by the polygonal image.
// Returns true if part is weak text and more than half of its area is
// intersected by parts from the part_list, and it is contained within im_box.
static bool TestWeakIntersectedPart(const TBOX& im_box,
ColPartition_LIST* part_list,
ColPartition* part) {
if (part->flow() < BTFT_STRONG_CHAIN) {
// A weak partition intersects the box.
TBOX part_box = part->bounding_box();
if (im_box.contains(part_box)) {
int area = part_box.area();
int intersect_area = IntersectArea(part_box, part_list);
if (area < 2 * intersect_area) {
return true;
}
}
}
return false;
}
// A rectangular or polygonal image has been completed, in part_list, bounding
// box in im_box. We want to eliminate weak text or other uncertain partitions
// (basically anything that is not BRT_STRONG_CHAIN or better) from both the
// part_grid and the big_parts list that are contained within im_box and
// overlapped enough by the possibly polygonal image.
static void EliminateWeakParts(const TBOX& im_box,
ColPartitionGrid* part_grid,
ColPartition_LIST* big_parts,
ColPartition_LIST* part_list) {
ColPartitionGridSearch rectsearch(part_grid);
ColPartition* part;
rectsearch.StartRectSearch(im_box);
while ((part = rectsearch.NextRectSearch()) != NULL) {
if (TestWeakIntersectedPart(im_box, part_list, part)) {
BlobRegionType type = part->blob_type();
if (type == BRT_POLYIMAGE || type == BRT_RECTIMAGE) {
rectsearch.RemoveBBox();
DeletePartition(part);
} else {
// The part is mostly covered, so mark it. Non-image partitions are
// kept hanging around to mark the image for pass2
part->set_flow(BTFT_NONTEXT);
part->set_blob_type(BRT_NOISE);
part->SetBlobTypes();
}
}
}
ColPartition_IT big_it(big_parts);
for (big_it.mark_cycle_pt(); !big_it.cycled_list(); big_it.forward()) {
part = big_it.data();
if (TestWeakIntersectedPart(im_box, part_list, part)) {
// Once marked, the blobs will be swept up by TidyBlobs.
DeletePartition(big_it.extract());
}
}
}
// Helper scans for good text partitions overlapping the given box.
// If there are no good text partitions overlapping an expanded box, then
// the box is expanded, otherwise, the original box is returned.
// If good text overlaps the box, true is returned.
static bool ScanForOverlappingText(ColPartitionGrid* part_grid, TBOX* box) {
ColPartitionGridSearch rectsearch(part_grid);
TBOX padded_box(*box);
padded_box.pad(kNoisePadding, kNoisePadding);
rectsearch.StartRectSearch(padded_box);
ColPartition* part;
bool any_text_in_padded_rect = false;
while ((part = rectsearch.NextRectSearch()) != NULL) {
if (part->flow() == BTFT_CHAIN ||
part->flow() == BTFT_STRONG_CHAIN) {
// Text intersects the box.
any_text_in_padded_rect = true;
TBOX part_box = part->bounding_box();
if (box->overlap(part_box)) {
return true;
}
}
}
if (!any_text_in_padded_rect)
*box = padded_box;
return false;
}
// Renders the boxes of image parts from the supplied list onto the image_pix,
// except where they interfere with existing strong text in the part_grid,
// and then deletes them.
// Box coordinates are rotated by rerotate to match the image.
static void MarkAndDeleteImageParts(const FCOORD& rerotate,
ColPartitionGrid* part_grid,
ColPartition_LIST* image_parts,
Pix* image_pix) {
if (image_pix == NULL)
return;
int imageheight = pixGetHeight(image_pix);
ColPartition_IT part_it(image_parts);
for (; !part_it.empty(); part_it.forward()) {
ColPartition* part = part_it.extract();
TBOX part_box = part->bounding_box();
BlobRegionType type = part->blob_type();
if (!ScanForOverlappingText(part_grid, &part_box) ||
type == BRT_RECTIMAGE || type == BRT_POLYIMAGE) {
// Mark the box on the image.
// All coords need to be rotated to match the image.
part_box.rotate(rerotate);
int left = part_box.left();
int top = part_box.top();
pixRasterop(image_pix, left, imageheight - top,
part_box.width(), part_box.height(), PIX_SET, NULL, 0, 0);
}
DeletePartition(part);
}
}
// Locates all the image partitions in the part_grid, that were found by a
// previous call to FindImagePartitions, marks them in the image_mask,
// removes them from the grid, and deletes them. This makes it possble to
// call FindImagePartitions again to produce less broken-up and less
// overlapping image partitions.
// rerotation specifies how to rotate the partition coords to match
// the image_mask, since this function is used after orientation correction.
void ImageFind::TransferImagePartsToImageMask(const FCOORD& rerotation,
ColPartitionGrid* part_grid,
Pix* image_mask) {
// Extract the noise parts from the grid and put them on a temporary list.
ColPartition_LIST parts_list;
ColPartition_IT part_it(&parts_list);
ColPartitionGridSearch gsearch(part_grid);
gsearch.StartFullSearch();
ColPartition* part;
while ((part = gsearch.NextFullSearch()) != NULL) {
BlobRegionType type = part->blob_type();
if (type == BRT_NOISE || type == BRT_RECTIMAGE || type == BRT_POLYIMAGE) {
part_it.add_after_then_move(part);
gsearch.RemoveBBox();
}
}
// Render listed noise partitions to the image mask.
MarkAndDeleteImageParts(rerotation, part_grid, &parts_list, image_mask);
}
// Removes and deletes all image partitions that are too small to be worth
// keeping. We have to do this as a separate phase after creating the image
// partitions as the small images are needed to join the larger ones together.
static void DeleteSmallImages(ColPartitionGrid* part_grid) {
if (part_grid != NULL) return;
ColPartitionGridSearch gsearch(part_grid);
gsearch.StartFullSearch();
ColPartition* part;
while ((part = gsearch.NextFullSearch()) != NULL) {
// Only delete rectangular images, since if it became a poly image, it
// is more evidence that it is somehow important.
if (part->blob_type() == BRT_RECTIMAGE) {
const TBOX& part_box = part->bounding_box();
if (part_box.width() < kMinImageFindSize ||
part_box.height() < kMinImageFindSize) {
// It is too small to keep. Just make it disappear.
gsearch.RemoveBBox();
DeletePartition(part);
}
}
}
}
// Runs a CC analysis on the image_pix mask image, and creates
// image partitions from them, cutting out strong text, and merging with
// nearby image regions such that they don't interfere with text.
// Rotation and rerotation specify how to rotate image coords to match
// the blob and partition coords and back again.
// The input/output part_grid owns all the created partitions, and
// the partitions own all the fake blobs that belong in the partitions.
// Since the other blobs in the other partitions will be owned by the block,
// ColPartitionGrid::ReTypeBlobs must be called afterwards to fix this
// situation and collect the image blobs.
void ImageFind::FindImagePartitions(Pix* image_pix,
const FCOORD& rotation,
const FCOORD& rerotation,
TO_BLOCK* block,
TabFind* tab_grid,
ColPartitionGrid* part_grid,
ColPartition_LIST* big_parts) {
int imageheight = pixGetHeight(image_pix);
Boxa* boxa;
Pixa* pixa;
ConnCompAndRectangularize(image_pix, &boxa, &pixa);
// Iterate the connected components in the image regions mask.
int nboxes = boxaGetCount(boxa);
for (int i = 0; i < nboxes; ++i) {
l_int32 x, y, width, height;
boxaGetBoxGeometry(boxa, i, &x, &y, &width, &height);
Pix* pix = pixaGetPix(pixa, i, L_CLONE);
TBOX im_box(x, imageheight -y - height, x + width, imageheight - y);
im_box.rotate(rotation); // Now matches all partitions and blobs.
ColPartitionGridSearch rectsearch(part_grid);
rectsearch.SetUniqueMode(true);
ColPartition_LIST part_list;
DivideImageIntoParts(im_box, rotation, rerotation, pix,
&rectsearch, &part_list);
if (textord_tabfind_show_images) {
pixWrite("junkimagecomponent.png", pix, IFF_PNG);
tprintf("Component has %d parts\n", part_list.length());
}
pixDestroy(&pix);
if (!part_list.empty()) {
ColPartition_IT part_it(&part_list);
if (part_list.singleton()) {
// We didn't have to chop it into a polygon to fit around text, so
// try expanding it to merge fragmented image parts, as long as it
// doesn't touch strong text.
ColPartition* part = part_it.extract();
TBOX text_box(im_box);
MaximalImageBoundingBox(part_grid, &text_box);
while (ExpandImageIntoParts(text_box, &rectsearch, part_grid, &part));
part_it.set_to_list(&part_list);
part_it.add_after_then_move(part);
im_box = part->bounding_box();
}
EliminateWeakParts(im_box, part_grid, big_parts, &part_list);
// Iterate the part_list and put the parts into the grid.
for (part_it.move_to_first(); !part_it.empty(); part_it.forward()) {
ColPartition* image_part = part_it.extract();
im_box = image_part->bounding_box();
part_grid->InsertBBox(true, true, image_part);
if (!part_it.at_last()) {
ColPartition* neighbour = part_it.data_relative(1);
image_part->AddPartner(false, neighbour);
neighbour->AddPartner(true, image_part);
}
}
}
}
boxaDestroy(&boxa);
pixaDestroy(&pixa);
DeleteSmallImages(part_grid);
if (textord_tabfind_show_images) {
ScrollView* images_win_ = part_grid->MakeWindow(1000, 400, "With Images");
part_grid->DisplayBoxes(images_win_);
}
}
} // namespace tesseract.
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