image - How to draw on an image in openGL?

Question

I load an image (biological image scans) and want to a) display it and b) draw markers on it. How would I program the shaders? I guess the vertex shaders are simple enough, since it is an 2D image. On idea I had was to overwrite the image data in the buffer, the pixels with the markers set to a specific values. My markers are boxes (so lines), is this the right way to go? I read that there are different primitives, lines too, so is there a way to draw my lines on my image without manipulating the data in the buffer, simply an overlay, so to speak? My framework is vispy, but pseudocode would also help.

Answer 1

用您的图像绘制一个矩形/正方形作为纹理。然后，绘制标记（可能是单调四边形/矩形）。

如果您希望线条在图像上方，但在标记下方，只需将渲染代码放在两者之间。

如果较旧的 OpenGL 适合您，则不需要着色器（因为 OpenGL 3.3 大多数旧的东西已移至兼容性配置文件，而现代功能是核心配置文件；后者需要自行编写的着色器，但它们对于您的情况应该很简单） .

总而言之，您需要了解的内容是图元（线、三角形）和基本纹理。