使用OpenCV提取矩阵

我在使用OpenCV提取矩阵（裁剪）时遇到了一些麻烦。有趣的是，如果我不执行该行来“裁剪”图像，则一切正常。但是，如果这样做，我会在图像的位置看到水平的彩色线条。

这是为了表明正确进行了裁剪。

cv::imshow("before", newimg);

//the line that "crops" the image
newimg = newimg(cv::Rect(leftcol, toprow, rightcol - leftcol, bottomrow - toprow));

cv::imshow("after", newimg);

接下来的代码是将图像绑定到纹理的位置，以便可以在OpenGL中使用它。

glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, newimg.cols, newimg.rows,
    0, GL_BGR, GL_UNSIGNED_BYTE, newimg.ptr());
glBindTexture(GL_TEXTURE_2D, 0);

以后再画。。。

float h = size;
float w = size * aspectRatio; // of the image. aspectRatio = width / height
glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glBindTexture(GL_TEXTURE_2D, texture);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(x, y, z);
glTexCoord2f(0.0f, 1.0f); glVertex3f(x, y + h, z);
glTexCoord2f(1.0f, 1.0f); glVertex3f(x + w, y + h, z);
glTexCoord2f(1.0f, 0.0f); glVertex3f(x + w, y, z);
glEnd();
glDisable(GL_TEXTURE_2D);

All of this works well and I see the proper image drawn in the OpenGL window when I comment out that line in which I had cropped the image. I have checked the image type before and after the cropping, but the only difference seems to be the reduced number of rows and columns in the final image.

Here is the image that gets drawn when cropping has been done.