I'm trying to wrap a C++ class which uses OpenCv so that I can use it in C#.
I have the C++ function:
void ImageBrightener::BrightenImage(const cv::Mat& sourceImage, cv::Mat& targetImage, int maxTarget)
{
double scaleFactor;
double shiftFactor = 0;
double minVal = DBL_MAX, minValTemp;
double maxVal = -DBL_MAX, maxValTemp;
auto numPixels = 0;
const auto RANGE_TOP_EXTEND = 10;
const auto RANGE_BOTTOM_EXTEND = 7;
assert(sourceImage.type() == CV_8UC1);
assert(sourceImage.channels() == 1);
cv::minMaxIdx(sourceImage, &minValTemp, &maxValTemp);
if (minValTemp < minVal)
minVal = minValTemp;
if (maxValTemp>maxVal)
maxVal = maxValTemp;
numPixels += sourceImage.cols * sourceImage.rows;
if (maxVal == minVal)
{
sourceImage.convertTo(targetImage, CV_8UC1, 1, shiftFactor);
return;
}
// Account for prev/curr ROI differences - add a bit to the range
maxVal += RANGE_TOP_EXTEND;
minVal -= RANGE_BOTTOM_EXTEND;
minVal = std::max(minVal, 0.);
if ((maxVal - minVal) < maxTarget)
{
scaleFactor = maxTarget / (maxVal - minVal);
shiftFactor = -1 * scaleFactor * minVal;
sourceImage.convertTo(targetImage, CV_8UC1, scaleFactor, shiftFactor);
return;
}
auto fltMinVal = static_cast<float>(minVal) - 1;
auto fltMaxVal = static_cast<float>(maxVal) + 1;
// Check histogram
const unsigned int *currval;
#define BINS (100)
#define CUTOFF (0.00003)
#define RESCUTOFF (0.2)
int hist[BINS] = { 0 };
int bin;
numPixels += sourceImage.cols * sourceImage.rows;
for (auto rowIndex = 0; rowIndex < sourceImage.rows; rowIndex++)
{
currval = sourceImage.ptr<unsigned>(rowIndex, 0);
for (auto colIndex = 0; colIndex < sourceImage.cols; colIndex++)
{
bin = static_cast<int>((BINS - 1) * ((*currval - fltMinVal) / (fltMaxVal - fltMinVal)));
assert(bin >= 0 && bin < BINS);
hist[bin]++;
++currval;
}
}
double ratio;
auto sum = 0;
int i;
for (i = BINS - 1; i >= 0; i--)
{
sum += hist[i];
ratio = static_cast<double>(sum) / static_cast<double>(numPixels);
if (ratio > CUTOFF)
break;
}
if (static_cast<double>(BINS - i) / static_cast<double>(BINS) > RESCUTOFF)
fltMaxVal = fltMinVal + ((i + 2)*(fltMaxVal - fltMinVal)) / BINS;
// Account for prev/curr ROI differences - add a bit to the range
fltMaxVal += RANGE_TOP_EXTEND;
fltMinVal -= RANGE_BOTTOM_EXTEND;
fltMinVal = std::max(fltMinVal, 0.f);
scaleFactor = maxTarget / (fltMaxVal - fltMinVal);
shiftFactor = -1 * scaleFactor * fltMinVal;
sourceImage.convertTo(targetImage, CV_8UC1, scaleFactor, shiftFactor);
}
When I test this code using the following C++ code:
int main()
{
auto* m_imageBrightener = new ImageBrightener();
auto inputImage = cv::imread("E:\\ttt.png", CV_LOAD_IMAGE_UNCHANGED);
cv::Mat outputImage;
m_imageBrightener->BrightenImage(inputImage, outputImage, 2000);
cv::imwrite("E:\\new_ttt.png", outputImage);
}
Everything works, the code does what it should, which is to get a dark 8bit image, and brighten it (I tried replacing 200 with 500 - it works fine). The new_ttt.png image is brightened as expected.
On the other hand, I have the following /Clr code, which wraps the C++ code and creates a DLL from it:
array<System::Byte>^ ImageProcessing::ImageBrightenerWrapper::BrightenImage(array<System::Byte>^ sourceImage, int imageWidth, int imageHeight, int maxTarget)
{
array<System::Byte>^ targetImage = (array<System::Byte>^)sourceImage->Clone();
pin_ptr<System::Byte> sourcePointer = &sourceImage[0];
pin_ptr<System::Byte> targetPointer = &targetImage[0];
cv::Mat sourceMat(imageHeight, imageWidth, CV_8UC1, (unsigned short*)sourcePointer);
cv::Mat targetMat(imageHeight, imageWidth, CV_8UC1, (unsigned short*)targetPointer);
targetMat.setTo(0);
m_imageBrightener->BrightenImage(sourceMat, targetMat, maxTarget);
uchar* tempPointer;
for (auto rowIndex = 0; rowIndex < imageHeight; ++rowIndex)
{
tempPointer = targetMat.ptr<uchar>(rowIndex);
for (auto colIndex = 0; colIndex < imageWidth; ++colIndex)
targetImage[rowIndex + colIndex] = tempPointer[colIndex];
}
return targetImage;
}
With it, I also have a WPF application which has a slider which controls the maxTarget parameter.
This is what I'm facing:
1) On the one hand, any value between 0 and 960 for maxTarget brightens the row index which matches maxTarget / 2 - Meaning, that when I slide the slider to the right, for greater values, I get part of the image bright and the rest is as the original. (Example: if maxTarget is 300, then all of the rows between row #0 and row #150 will be brighter and the rest will be like the original).
2) On the other hand, if I cross the value if 960 for maxTarget then the application crashes with the following error (even though the code is surrounded with try/catch):
"An exception of type: 'System.AccessViolationException' occurred in ImageBrightenerWrapper.dll but was not handled in user code. Additional information: Attempted to read or write protected memory. This is pften an indication that other memory is corrupt."
What am I doing wrong here?