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Topic: Bitmap clipper & plotter (BASIC prototypes) (Read 1241 times) |
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admin
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Re: Bitmap clipper & plotter (BASIC prototypes)
« Reply #5 on: Mar 5th, 2012, 4:44pm » |
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on Mar 5th, 2012, 03:18am, David Williams wrote:| DrawIconRTR alphablends on a pixel-by-pixel basis (using the alpha value of each source bitmap pixel, and pre-multiplied alphas of background pixels). |
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I don't really know what you mean by "pre-multiplied alphas of background pixels" here. In what sense do 'background' pixels have an alpha anyway? I don't guarantee that my routine will do anything sensible with the 'alpha' byte in the background bitmap: it may well corrupt it. I treat it as a 'don't care' byte.
Quote:| So the two routines do quite similar things |
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Does yours have the 'reflect' (about either axis) option? That added a significant degree of complexity, as I recollect.
My routine is, of course, optimised for no clipping, since (at least in my applications) clipping is very much an exceptional case.
Richard.
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| « Last Edit: Mar 5th, 2012, 4:54pm by admin » |
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David Williams
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Re: Bitmap clipper & plotter (BASIC prototypes)
« Reply #6 on: Mar 6th, 2012, 03:21am » |
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on Mar 5th, 2012, 4:44pm, Richard Russell wrote:| I don't really know what you mean by "pre-multiplied alphas of background pixels" here. |
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Neither do I (lol).
I now know that what I wrote was nonsense.
on Mar 5th, 2012, 4:44pm, Richard Russell wrote:| Does yours have the 'reflect' (about either axis) option? That added a significant degree of complexity, as I recollect. |
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No, mine doesn't.
The only GFXLIB routine that performs any kind of flipping/reflection is GFXLIB_PlotFlip (and a variant of it). This may be about to change, however.
David.
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