Quickie on ReadPixel(x,y)
Blitz3D Forums/Blitz3D Beginners Area/Quickie on ReadPixel(x,y)
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| Wotcha, folks. Can anyone tell me why the command ReadPixel(x,y) returns numbers like -65536 for red pixels and -16777216 for black pixels? I was expecting something like 255,0,0 or 0,0,0. Many thanks. Tobo |
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| http://www.blitzbasic.com/codearcs/codearcs.php?code=551 |
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| R Tape loading error, 0:1 ....ahhh, a Spectrum man. Cheers, Rob. That'll come in handy, mate. The original numbers it gives out, do they actually mean anything though? Tobo |
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| ARGB as a 32 bit number First 8 bits are alpha (0-255) Next 8 are red (0-255) Next 8 are green (0-255) Next 8 and Blue (0-255) Hence all the bit shifts in the functions. |
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| Isn't there GetColor or something for this? |
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| As Rob said, www.blitzbasic.com/codearcs/codearcs.php?code=551 |
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| Will those functions work for all cards? I remember Docs saying something about locking buffers to prevent crashing. How can they be altered to Lock buffers??? |
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| use readpixelfast and writepixelfast for locked buffers. I tend to use them using read/writepixelfast, also you might want to combine the read_r/g/b into one function and load the results into 3 globals so you only do a single readpixelfast to get all r,g and b values. The functions I've put in the code archives are just simplified for ease of use. They can be optimised dramatically. |
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| And definitely use the readpixelfast/writepixelfast functions on locked buffers. The speed improvement is NOT insignificant. |
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