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| Use magenta as transparent color |
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Diego Barboza
Member #16,292
April 2016
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Hello everyone! Is there a way to specify color to use as a transparency mask for a bitmap in Allegro 5? I'm creating some bitmaps at run-time and based on a previously acquired image with no alpha channel (these images are also acquired at run-time). So, I use magenta (255, 0, 255) as a key color and I'm trying to replace this for alpha == 0. This gives me the expected effect, but it's very slow. Is it possible by any means to tell Allegro to always use magenta as transparency? al_convert_mask_to_alpha(buffer, al_map_rgb(255, 0, 255)); Thanks in advance, |
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jmasterx
Member #11,410
October 2009
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Agui GUI API -> https://github.com/jmasterx/Agui |
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Diego Barboza
Member #16,292
April 2016
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jmasterx, thanks for the link, but as I said on my initial post, I've already tested this function and it's too slow to use every time I create a new bitmap. |
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jmasterx
Member #11,410
October 2009
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You should probably create your bitmaps as ALLEGRO_MEMORY bitmaps, apply the mask conversion, then convert to video. If they are created as video, then to alter it, you have to do a lot of extra work. If none of that works, the more modern solution might be to apply a shader when you render these bitmaps. The shader logic is: if(pixelcolor == magic pink) return color(0,0,0,0) else return pixelcolor The other option is, if you can, before creating the allegro bitmaps, remove the pink from whatever memory buffer you're creating them from. Agui GUI API -> https://github.com/jmasterx/Agui |
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Peter Hull
Member #1,136
March 2001
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How slow is too slow? I did some quick checking and it takes about 4 milliseconds on my laptop to call al_convert_mask_to_alpha(buffer, al_map_rgb(255, 0, 255)) on a 256x256 bitmap. You may be able to get quicker if you use al_lock_bitmap and roll your own conversion. Pete
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l j
Member #10,584
January 2009
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At "run-time" is quite vague. Are you generating them in real-time or something?
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David Couzelis
Member #10,079
August 2008
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Diego Barboza said: This gives me the expected effect, but it's very slow. That's why I use a set of helper functions I wrote (in C): https://github.com/drcouzelis/colorwandcastle/blob/master/src/resources.h https://github.com/drcouzelis/colorwandcastle/blob/master/src/resources.c The code IMG("filename.png"); will return a pointer to an ALLEGRO_BITMAP. The first time you use that filename it is loaded from the hard drive into memory. After that, every time you load the same filename it just reuses the bitmap that's already been loaded into memory. |
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Peter Hull
Member #1,136
March 2001
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David Couzelis said: The first time you use that filename it is loaded from the hard drive good, apart from... Diego Barboza said: I'm creating some bitmaps at run-time DB could you give us some more detail on how, and how often, these bitmaps are created?
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David Couzelis
Member #10,079
August 2008
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Oh wow, I totally misunderstood the situation. Please consider disregarding me! |
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Diego Barboza
Member #16,292
April 2016
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Hi everyone, I'm making a video streaming application, so these bitmaps are generated every frame. I followed jmasterx's advice and used a shader. It's pretty easy to implement and it's very fast! Thank you all! |
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