readpixel return negative value !
BlitzPlus Forums/BlitzPlus Programming/readpixel return negative value !
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| Hi ! i don't understand why in this case readpixel return a negative value, not an integer. Could you help me please ? I just want read the pixel color at x,y and compare it to 255,0,255 ! Thanks !
load 8 or 24 bits png image as mask
Mask = LoadImage ("masque.png")
...
col = ReadPixel (x,y, ImageBuffer(Mask)
(rgb = 255,0,255)
MaskColor = 255 Or (0 Shl 8) Or (255 Shl 16)
if MaskColor = col then
;collision
end if
...
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| The first 8 bits are alpha. This is used in textures. When ReadPixel is used on an image the alpha value is always 255. This corresponds to fully opaque. ReadPixel(x,y) And $FFFFFF This zeroes out the first 8 bits and gives the RGB value you expect. |
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| col = ReadPixel (x,y, ImageBuffer(Mask) And $FFFFFF should do it. Strips the alpha values which can make it appear like a negative. |
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| Thanks Floyd & MasterBeaker ! |
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