Strip alpha from pixels above 0
BlitzMax Forums/BlitzMax Beginners Area/Strip alpha from pixels above 0
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| I have a PNG loaded into a pixmap, I need to loop through it and change any pixels that are not totally transparent to being solid. Everything I try seems to crash, I think somehow readpixel or writepixel is getting out of the application memory and windows is... less than happy about that... Though it seems to work when I do it once, but then when I do it a second time to a different pixmap, or even the same one, it crashes... Does anyone have a sample they can share? |
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| can you post some code? |
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Your probably doing something like this?
For Local y:Int = 0 To pixmap.Height
For Local x:Int = 0 To pixmap.Width
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IE, using To instead of Until (or forgetting to -1) Either way, using ReadPixel() and WritePixel() when your going to access the whole pixmap isnt realy necessary. Try this instead: Function StripPartialAlpha( px:TPixmap) If Not px Then Return Local p:Byte Ptr = px.Pixels Local stop:Byte Ptr = p + px.Capacity Select px.Format Case PF_RGBA8888 While p < stop If p[3] > 0 Then p[3] = 255 p :+ 4 Wend Case PF_BGRA8888 While p < stop If p[0] > 0 Then p[0] = 255 p :+ 4 Wend EndSelect EndFunction |
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| I was using To, I still have no idea what I was doing wrong, but your function is way faster and best of all it works! thank you! |
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| You could do it a lot faster than that but it looks like it would work. You shouldn't be looping TO pixmap.Height, you should be going Until pixmap.Height Same for the width. And if you compile with debug on it should be telling you something? |
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