QT5 with OpenGL and Kinect v2: wrong image presentation - c++

Question

I would like to show a color image from the kinect v2 sensor over openGl in a Qt widget. The problem is, that the presentation of this image is incorrect.
Here is the code where I get the color frame:
class:
cv::Mat ColorMap;
std::vector<BYTE> colorBuffer;
int color_width;
int color_height;
code:
if(colorBuffer.empty())
colorBuffer.resize(color_height * color_width * 4 * sizeof(unsigned char));
hr = ColorFrame->CopyConvertedFrameDataToArray((UINT)colorBuffer.size(),
&colorBuffer[0], ColorImageFormat::ColorImageFormat_Bgra );
ColorMap = cv::Mat( color_height, color_width, CV_8UC4, &colorBuffer[0]);
That means, I get the color information as BGR Format with an alpha channel and copy it to a matrix with 4 channels, (BRGA) and each channel has 8Bit from 0 to 255. Correct?
In the next step, I resize it as the same size as the widget:
Kinect->CreateFrame();
cv::Mat GUIColorImage;
Kinect->ColorMap.copyTo(GUIColorImage);
cv::resize(GUIColorImage,GUIColorImage,
cv::Size(ui->Left_Widget_Color->width(),ui->Left_Widget_Color->height()));
Than I've tried two convert methods:
1. convert to BGR
2. convert to 8UC3 (8-Bit, unsigned char, 3 channels (the same as BGR?))
1: GUIColorImage.convertTo(GUIColorImage,CV_BGRA2BGR);
2: GUIColorImage.convertTo(GUIColorImage,CV_8UC3);
But no solutions works.
After the conversion, I try to display it over openGl with:
LeftWidgetColor.UpdateImage(GUIColorImage);
LeftWidgetColor is a QOpenGLWidget:
header:
class RenderWidget : public QOpenGLWidget
{
Q_OBJECT
public:
RenderWidget(QWidget *parent);
~RenderWidget();
void UpdateImage(cv::Mat newimage);
void initializeGL();
void paintGL();
private:
int width;
int height;
GLuint texture;
cv::Mat image;
signals:
void info(QString msg);
void error(QString msg);
void DepthValueAt(cv::Point2i DepthPosition);
protected:
void mousePressEvent(QMouseEvent *event);
void mouseReleaseEvent(QMouseEvent *event);
void mouseMoveEvent(QMouseEvent *event);
};
code:
RenderWidget::RenderWidget(QWidget *parent) : QOpenGLWidget(parent)
{
width = this->size().width();
height = this->size().height();
texture = 0;
initializeGL();
}
RenderWidget::~RenderWidget()
{
glDeleteTextures(1, &texture);
}
void RenderWidget::initializeGL()
{
//Background Color is black
glClearColor(0,0,0,1);
//Storage of Pixelmode for two-dimensional textures
glPixelStorei (GL_UNPACK_ALIGNMENT, 1);
//Create texture
glGenTextures(1, &texture);
glViewport(0, 0, width, height);
}
void RenderWidget::paintGL()
{
// Clear the screen and depth buffer (with black)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Select the model view matrix and reset it
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0f, 0.0f, 0.0f);
// Abort drawing if OpenCV was unable to open the camera
if (image.empty())
{
return;
}
glEnable(GL_TEXTURE_RECTANGLE_ARB);
// Typical texture generation using data from the bitmap
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture);
// Transfer image data to the GPU
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
3, image.cols, image.rows, 0,
GL_BGR, GL_UNSIGNED_BYTE, image.data);
if (glGetError() != GL_NO_ERROR)
{
}
// Draw a 2D face with texture
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex2f(1, 1);
glTexCoord2f(image.cols, 0); glVertex2f(-1, 1);
glTexCoord2f(image.cols, image.rows); glVertex2f(-1, -1);
glTexCoord2f(0, image.rows); glVertex2f(1, -1);
glEnd();
glDisable(GL_TEXTURE_RECTANGLE_ARB);
}
void RenderWidget::UpdateImage(cv::Mat newimage)
{
newimage.copyTo(image);
update();
}
I guess the problem is in:
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
3, image.cols, image.rows, 0,
GL_BGR, GL_UNSIGNED_BYTE, image.data);
But I can't find it. I've declared 3-channels, BGR, 8-Bit = 1 Byte as unsigned. Does someone know where the mistake is?
If i show it over imshow (openCv class), it works fine.

Answer 1

My Mistake was, that I used cv::Mat::convertTo(): but here
they wrote, that convertTo() should not used to convert the format (Only to change the data type). cv::cvtColor is the right function and it works well for me. So I've changed the conversion from:
GUIColorImage.convertTo(GUIColorImage,CV_BGRA2BGR);
to
cv::cvtColor(GUIColorImage,GUIColorImage,CV_BGRA2BGR);