I want to count how many distinct colors I have in a bitmap. For this I have a pointer to Scan0 where the bitmap pixels are located, the number of pixels, a buffer to store all distinct colors found in the image and a buffer that will store how many times each color have been found. These last two buffers are the same size as the pixel data - assuming the worst case that each pixel in the image have a different color.
mov esi, [esp + 4] ; Scan0 - pointer to the bitmap pixels
mov ecx, [esp + 8] ; Number of pixels in buffer
mov edi, [esp + 12] ; Pointer to a buffer that will store each distinct color
mov ebx, [esp + 16] ; Pointer to a buffer that will store how many times each color has been found
xor edx, edx ; EDX - will be used to keep tracking the offset (how many distinct colors have been found so far)
NextPixel:
lodsd
push ecx
mov ecx, edx
NextCheck:
cmp ecx, 0
je AddColor
cmp eax, [edi + ecx * 4]
je UpdateIndex
loop NextCheck
AddColor:
mov dword[edi + edx * 4], eax
mov dword[ebx + edx * 4], 1
inc edx
pop ecx
loop NextPixel
jmp Exit
UpdateIndex:
add dword[ebx + ecx], 1
pop ecx
jmp NextPixel
Exit:
ret 16
Well, I wrote this code but it's not working and sometimes even crash. Any thoughts what I am doing wrong?
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> Main > Count number of distinct colors in a buffer
27 May 2022, 15:00