Qt 5 and OpenCV 4 Computer Vision Projects

Drawing images with OpenGL

In order to draw an image on the OpenGL viewport, we should introduce another concept of OpenGL—the texture. A texture in OpenGL is usually a 2D image, and it is generally used to add visual detail to an object, which is mainly a triangle.

Since any kind of digital image is usually a rectangle, we should draw two triangles to compose a rectangle for the image, and then load the image as a texture and map it to the rectangles.

The texture uses a coordinate system that differs from the NDC that is used when we draw the triangles. Both of the x and y (axes) of the texture coordinate system are between 0 and 1, that is, the bottom-left corner is (0, 0), while the top-right corner is (1, 1). So, our vertices and coordinate ...