Memory Access violation when saving a png image #6198
Description
Hi I'm using opencv 3 (x86) in windows 10 , I tried also to compile the 3.1 version but I have the same problem.
I'm getting an exception when saving a png image with 4 channels.
Here is the code (is the example in the docs):
#include <vector>
#include <stdio.h>
#include <opencv2/opencv.hpp>
using namespace cv;
using namespace std;
void createAlphaMat(Mat &mat)
{
for (int i = 0; i < mat.rows; ++i) {
for (int j = 0; j < mat.cols; ++j) {
Vec4b& rgba = mat.at<Vec4b>(i, j);
rgba[0] = UCHAR_MAX;
rgba[1] = saturate_cast<uchar>((float(mat.cols - j)) / ((float)mat.cols) * UCHAR_MAX);
rgba[2] = saturate_cast<uchar>((float(mat.rows - i)) / ((float)mat.rows) * UCHAR_MAX);
rgba[3] = saturate_cast<uchar>(0.5 * (rgba[1] + rgba[2]));
}
}
}
int main(int argv, char **argc)
{
// Create mat with alpha channel
Mat mat(480, 640, CV_8UC4);
createAlphaMat(mat);
vector<int> compression_params;
compression_params.push_back(16);
compression_params.push_back(9);
try {
imwrite("alpha.png", mat, compression_params);
}
catch (runtime_error& ex) {
fprintf(stderr, "Exception converting image to PNG format: %s\n", ex.what());
return 1;
}
fprintf(stdout, "Saved PNG file with alpha data.\n");
return 0;
}
I get a memory access violation and the debugger stops in grfmt_png.cpp at line 380, around here:
...
bool isBilevel = false;
for( size_t i = 0; i < params.size(); i += 2 )
{
if( params[i] == CV_IMWRITE_PNG_COMPRESSION )
{
compression_level = params[i+1];
compression_level = MIN(MAX(compression_level, 0), Z_BEST_COMPRESSION);
}
...