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allow to retrieve videocapture properties before first frame reading

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This commit is contained in:
Ilya Lavrenov 2015-10-26 14:37:38 +03:00
parent 95d6002f16
commit 9d78a1ea9f
1 changed files with 25 additions and 5 deletions
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30
modules/highgui/src/cap_images.cpp
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@ -67,10 +67,11 @@ class CvCapture_Images : public CvCapture
public: public:
CvCapture_Images() CvCapture_Images()
{ {
filename = 0; filename = NULL;
currentframe = firstframe = 0; currentframe = firstframe = 0;
length = 0; length = 0;
frame = 0; frame = NULL;
grabbedInOpen = false;
} }
virtual ~CvCapture_Images() virtual ~CvCapture_Images()
@ -92,6 +93,7 @@ protected:
unsigned length; // length of sequence unsigned length; // length of sequence
IplImage* frame; IplImage* frame;
bool grabbedInOpen;
}; };
@ -100,7 +102,7 @@ void CvCapture_Images::close()
if( filename ) if( filename )
{ {
free(filename); free(filename);
filename = 0; filename = NULL;
} }
currentframe = firstframe = 0; currentframe = firstframe = 0;
length = 0; length = 0;
@ -113,6 +115,14 @@ bool CvCapture_Images::grabFrame()
char str[_MAX_PATH]; char str[_MAX_PATH];
sprintf(str, filename, firstframe + currentframe); sprintf(str, filename, firstframe + currentframe);
if (grabbedInOpen)
{
grabbedInOpen = false;
++currentframe;
return true;
}
cvReleaseImage(&frame); cvReleaseImage(&frame);
frame = cvLoadImage(str, CV_LOAD_IMAGE_ANYDEPTH | CV_LOAD_IMAGE_ANYCOLOR); frame = cvLoadImage(str, CV_LOAD_IMAGE_ANYDEPTH | CV_LOAD_IMAGE_ANYCOLOR);
if( frame ) if( frame )
@ -123,7 +133,7 @@ bool CvCapture_Images::grabFrame()
IplImage* CvCapture_Images::retrieveFrame(int) IplImage* CvCapture_Images::retrieveFrame(int)
{ {
return frame; return grabbedInOpen ? NULL : frame;
} }
double CvCapture_Images::getProperty(int id) double CvCapture_Images::getProperty(int id)
@ -166,6 +176,8 @@ bool CvCapture_Images::setProperty(int id, double value)
value = length - 1; value = length - 1;
} }
currentframe = cvRound(value); currentframe = cvRound(value);
if (currentframe != 0)
grabbedInOpen = false; // grabbed frame is not valid anymore
return true; return true;
case CV_CAP_PROP_POS_AVI_RATIO: case CV_CAP_PROP_POS_AVI_RATIO:
if(value > 1) { if(value > 1) {
@ -176,6 +188,8 @@ bool CvCapture_Images::setProperty(int id, double value)
value = 0; value = 0;
} }
currentframe = cvRound((length - 1) * value); currentframe = cvRound((length - 1) * value);
if (currentframe != 0)
grabbedInOpen = false; // grabbed frame is not valid anymore
return true; return true;
} }
CV_WARN("unknown/unhandled property\n"); CV_WARN("unknown/unhandled property\n");
@ -278,6 +292,12 @@ bool CvCapture_Images::open(const char * _filename)
} }
firstframe = offset; firstframe = offset;
// grab frame to enable properties retrieval
grabFrame();
grabbedInOpen = true;
currentframe = 0;
return true; return true;
} }
@ -290,7 +310,7 @@ CvCapture* cvCreateFileCapture_Images(const char * filename)
return capture; return capture;
delete capture; delete capture;
return 0; return NULL;
} }
// //