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idinkin

Alpha channel

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What is the best format that is supported by photoshop that stores the 4 channels: Red, Green, Blue, Alpha? Does it use compression? What size a 512x512 image will take about?

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Well, there's TGAs, but they generally aren't compressed. There is compression available for the format, but I've never used it.

There's also multiple 3rd party utilities available for converting files to DXTC formats.

[edited by - Ostsol on October 24, 2003 1:51:50 PM]

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I like TGA''s. I have a tga loader that can read 16, 24 and 32 bit uncompressed RGB(A), and 16, 24 and 32 bit RLE images. The RLE works really well if you have an image that uses alot of the same color in a row (it stores it in a value, with a count of how many times to repeat it). If you have a photograph type image though, RLE sucks, because you have to have the packet to tell you how many to repeat, and if it is only one (a raw packet), then you might even increase the size of your file. For stuff you make in photoshop though, it''ll probably be sufficient.

I''ve heard good things about PNG files as well. They have lossless compression (unlike JPEG and the like), and they support having an alpha channel. I''ve never tried PNG''s yet, but you might look into it. It even has its own libraries (I think you have to get zlib and libpng).

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I made my own ".tex" format: 1 dword header, 3 ints - width, height, numchannels + data



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quote:
Original post by idinkin
How do you think what is the smallest/normal quality format for gray scale images?


Gray scale images are obviously 8 bit images...the best format is GIF!! Unfortunately It''s licensed and it is hard (and illegal I suppose)to get source/library to use them. Fortunately GIF are based on an algorithm similar to zlib so you can use this lib to compress data (without losses).
Of course you should create an header of your own...another solution is to use BMP (without compression).

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quote:
Original post by blizzard999
quote:
Original post by idinkin
How do you think what is the smallest/normal quality format for gray scale images?


Gray scale images are obviously 8 bit images...the best format is GIF!! Unfortunately It''s licensed and it is hard (and illegal I suppose)to get source/library to use them. Fortunately GIF are based on an algorithm similar to zlib so you can use this lib to compress data (without losses).
Of course you should create an header of your own...another solution is to use BMP (without compression).




PNG is supposedly the better alternative to gif, especially with the liscensing issues. They also corrected and added some features that gif didn''t.

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Just my two cents.

PNG has a similar licence as ZLib ((g)zip files). The compression is very similar (almost the same actually). As they say at the ZLib page (www.zlib.org):
quote:
If this page seems suspiciously similar to the PNG Home Page, rest assured that the similarity is completely coincidental. No, really.



And there is no data loss with zip files, so also none at png files.

This is the png site:
http://www.libpng.org/pub/png/


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