A View in our legacy application is displaying an image using StretchDIBits. In case you are not familiar with StretchDIBits, it is used to display an image with given size to another size on MFC View. For example, an image of size (128,120) can be displayed on (512,512) with the function.
In simple condition where width or height of display is multiple of that of the image, I can calculate location of a pixel in original image from location of the display without problem. But in the other case, I think I need to know how StretchDIBits distributes pixels from original image to display rectangle of given size, especially when there is no multiples between sizes of the two.
I don’t know how StretchDIBits maps input pixels to output pixels, and I suspect it’s subject to change at Microsoft’s whim anyway.
Create an image the same size as your input, and fill the pixels with incrementing values: (0,0) gets RGB(0,0,0), (0,1) gets RGB(0,1,0), (10,20) gets RGB(10,20,0), etc. Create a memory DC the same size as your output and use StretchDIBits to draw the image into it. Now every pixel in that DC can be mapped back to the input by the color it contains.