From f0ef7bd14913887f0021878b27d8dd9f2f90e8b7 Mon Sep 17 00:00:00 2001 From: Rostislav Vasilikhin Date: Thu, 10 Aug 2017 17:26:42 +0300 Subject: [PATCH] Lab and Luv tests: rewritten, constants explained --- modules/imgproc/test/test_color.cpp | 129 ++++++++++++++++------------ 1 file changed, 76 insertions(+), 53 deletions(-) diff --git a/modules/imgproc/test/test_color.cpp b/modules/imgproc/test/test_color.cpp index e920ad4646..deeeb8da91 100644 --- a/modules/imgproc/test/test_color.cpp +++ b/modules/imgproc/test/test_color.cpp @@ -1010,10 +1010,6 @@ double CV_ColorLabTest::get_success_error_level( int /*test_case_idx*/, int i, i } -static const double _1_3 = 0.333333333333; -const static float _1_3f = static_cast(_1_3); - - void CV_ColorLabTest::convert_row_bgr2abc_32f_c3(const float* src_row, float* dst_row, int n) { int depth = test_mat[INPUT][0].depth(); @@ -1021,6 +1017,15 @@ void CV_ColorLabTest::convert_row_bgr2abc_32f_c3(const float* src_row, float* ds float ab_bias = depth == CV_8U ? 128.f : depth == CV_16U ? 32768.f : 0.f; float M[9]; + // 7.787f = (29/3)^3/(29*4) + static const float lowScale = 29.f*29.f/(27.f*4.f); + // 0.008856f = (6/29)^3 + static const float lthresh = 6.f*6.f*6.f/(29.f*29.f*29.f); + // 903.3 = (29/3)^3 + static const float yscale = 29.f*29.f*29.f/27.f; + + static const float f16of116 = 16.f/116.f; + for (int j = 0; j < 9; j++ ) M[j] = (float)RGB2XYZ[j]; @@ -1031,25 +1036,14 @@ void CV_ColorLabTest::convert_row_bgr2abc_32f_c3(const float* src_row, float* ds float B = src_row[x]; float X = (R * M[0] + G * M[1] + B * M[2]) / Xn; - float Y = R * M[3] + G * M[4] + B * M[5]; + float Y = R * M[3] + G * M[4] + B * M[5]; float Z = (R * M[6] + G * M[7] + B * M[8]) / Zn; - float fX = X > 0.008856f ? pow(X, _1_3f) : - (7.787f * X + 16.f / 116.f); - float fZ = Z > 0.008856f ? pow(Z, _1_3f): - (7.787f * Z + 16.f / 116.f); - float L = 0.0f, fY = 0.0f; - if (Y > 0.008856f) - { - fY = pow(Y, _1_3f); - L = 116.f * fY - 16.f; - } - else - { - fY = 7.787f * Y + 16.f / 116.f; - L = 903.3f * Y; - } + float fX = X > lthresh ? cubeRoot(X) : (lowScale * X + f16of116); + float fY = Y > lthresh ? cubeRoot(Y) : (lowScale * Y + f16of116); + float fZ = Z > lthresh ? cubeRoot(Z) : (lowScale * Z + f16of116); + float L = Y > lthresh ? (116.f*fY - 16.f) : (yscale*Y); float a = 500.f * (fX - fY); float b = 200.f * (fY - fZ); @@ -1069,8 +1063,16 @@ void CV_ColorLabTest::convert_row_abc2bgr_32f_c3( const float* src_row, float* d for(int j = 0; j < 9; j++ ) M[j] = (float)XYZ2RGB[j]; - static const float lthresh = 903.3f * 0.008856f; - static const float thresh = 7.787f * 0.008856f + 16.0f / 116.0f; + // 0.008856f * 903.3f = (6/29)^3*(29/3)^3 = 8 + static const float lThresh = 8.f; + // 7.787f * 0.008856f + 16.0f / 116.0f = 6/29 + static const float fThresh = 6.f/29.f; + static const float lbias = 16.f/116.f; + // 7.787f = (29/3)^3/(29*4) + static const float lowScale = 29.f*29.f/(27.f*4.f); + // 903.3 = (29/3)^3 + static const float yscale = 29.f*29.f*29.f/27.f; + for (int x = 0, end = n * 3; x < end; x += 3) { float L = src_row[x] * Lscale; @@ -1078,10 +1080,10 @@ void CV_ColorLabTest::convert_row_abc2bgr_32f_c3( const float* src_row, float* d float b = src_row[x + 2] - ab_bias; float FY = 0.0f, Y = 0.0f; - if (L <= lthresh) + if (L <= lThresh) { - Y = L / 903.3f; - FY = 7.787f * Y + 16.0f / 116.0f; + Y = L / yscale; + FY = lowScale * Y + lbias; } else { @@ -1095,8 +1097,8 @@ void CV_ColorLabTest::convert_row_abc2bgr_32f_c3( const float* src_row, float* d float FXZ[] = { FX, FZ }; for (int k = 0; k < 2; ++k) { - if (FXZ[k] <= thresh) - FXZ[k] = (FXZ[k] - 16.0f / 116.0f) / 7.787f; + if (FXZ[k] <= fThresh) + FXZ[k] = (FXZ[k] - lbias) / lowScale; else FXZ[k] = FXZ[k] * FXZ[k] * FXZ[k]; } @@ -1155,25 +1157,37 @@ void CV_ColorLuvTest::convert_row_bgr2abc_32f_c3( const float* src_row, float* d { int depth = test_mat[INPUT][0].depth(); float Lscale = depth == CV_8U ? 255.f/100.f : depth == CV_16U ? 65535.f/100.f : 1.f; + static const float uLow = -134.f, uHigh = 220.f, uRange = uHigh - uLow; + static const float vLow = -140.f, vHigh = 122.f, vRange = vHigh - vLow; int j; float M[9]; - float un = 4.f*Xn/(Xn + 15.f*1.f + 3*Zn); - float vn = 9.f*1.f/(Xn + 15.f*1.f + 3*Zn); + // Yn == 1 + float dd = Xn + 15.f*1.f + 3.f*Zn; + float un = 4.f*13.f*Xn/dd; + float vn = 9.f*13.f/dd; + float u_scale = 1.f, u_bias = 0.f; float v_scale = 1.f, v_bias = 0.f; for( j = 0; j < 9; j++ ) M[j] = (float)RGB2XYZ[j]; + //0.72033 = 255/(220+134), 96.525 = 134*255/(220+134) + //0.9732 = 255/(140+122), 136.259 = 140*255/(140+122) if( depth == CV_8U ) { - u_scale = 0.720338983f; - u_bias = 96.5254237f; - v_scale = 0.973282442f; - v_bias = 136.2595419f; + u_scale = 255.f/uRange; + u_bias = -uLow*255.f/uRange; + v_scale = 255.f/vRange; + v_bias = -vLow*255.f/vRange; } + // 0.008856f = (6/29)^3 + static const float lthresh = 6.f*6.f*6.f/(29.f*29.f*29.f); + // 903.3 = (29/3)^3 + static const float yscale = 29.f*29.f*29.f/27.f; + for( j = 0; j < n*3; j += 3 ) { float r = src_row[j+2]; @@ -1189,14 +1203,14 @@ void CV_ColorLuvTest::convert_row_bgr2abc_32f_c3( const float* src_row, float* d L = u = v = 0; else { - if( Y > 0.008856f ) - L = (float)(116.*pow((double)Y,_1_3) - 16.); + if( Y > lthresh ) + L = 116.f*cubeRoot(Y) - 16.f; else - L = 903.3f * Y; + L = yscale * Y; - d = 1.f/d; - u = 13*L*(4*X*d - un); - v = 13*L*(9*Y*d - vn); + d = 4.f*13.f/d; + u = L*(X*d - un); + v = L*(9.f/4.f*Y*d - vn); } dst_row[j] = L*Lscale; dst_row[j+1] = u*u_scale + u_bias; @@ -1209,24 +1223,34 @@ void CV_ColorLuvTest::convert_row_abc2bgr_32f_c3( const float* src_row, float* d { int depth = test_mat[INPUT][0].depth(); float Lscale = depth == CV_8U ? 100.f/255.f : depth == CV_16U ? 100.f/65535.f : 1.f; + static const float uLow = -134.f, uHigh = 220.f, uRange = uHigh - uLow; + static const float vLow = -140.f, vHigh = 122.f, vRange = vHigh - vLow; + int j; float M[9]; - float un = 4.f*Xn/(Xn + 15.f*1.f + 3*Zn); - float vn = 9.f*1.f/(Xn + 15.f*1.f + 3*Zn); + // Yn == 1 + float dd = Xn + 15.f*1.f + 3.f*Zn; + float un = 4*13.f*Xn/dd; + float vn = 9*13.f*1.f/dd; + float u_scale = 1.f, u_bias = 0.f; float v_scale = 1.f, v_bias = 0.f; for( j = 0; j < 9; j++ ) M[j] = (float)XYZ2RGB[j]; + //0.72033 = 255/(220+134), 96.525 = 134*255/(220+134) + //0.9732 = 255/(140+122), 136.259 = 140*255/(140+122) if( depth == CV_8U ) { - u_scale = 1.f/0.720338983f; - u_bias = 96.5254237f; - v_scale = 1.f/0.973282442f; - v_bias = 136.2595419f; + u_scale = uRange/255.f; + u_bias = -uLow*255.f/uRange; + v_scale = vRange/255.f; + v_bias = -vLow*255.f/vRange; } + // (1 / 903.3) = (3/29)^3 + static const float yscale = 27.f/(29.f*29.f*29.f); for( j = 0; j < n*3; j += 3 ) { float L = src_row[j]*Lscale; @@ -1241,16 +1265,15 @@ void CV_ColorLuvTest::convert_row_abc2bgr_32f_c3( const float* src_row, float* d } else { - Y = L * (1.f/903.3f); - if( L == 0 ) - L = 0.001f; + Y = L * yscale; } - u = u/(13*L) + un; - v = v/(13*L) + vn; - - X = -9*Y*u/((u - 4)*v - u*v); - Z = (9*Y - 15*v*Y - v*X)/(3*v); + float up = 3.f*(u + L*un); + float vp = 0.25f/(v + L*vn); + if(vp > 0.25f) vp = 0.25f; + if(vp < -0.25f) vp = -0.25f; + X = Y*3.f*up*vp; + Z = Y*(((12.f*13.f)*L - up)*vp - 5.f); float r = M[0]*X + M[1]*Y + M[2]*Z; float g = M[3]*X + M[4]*Y + M[5]*Z;