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AppGameKit Classic Chat / Image color depth & memory

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MikeMax
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Posted: 10th Mar 2012 19:51 Edited at: 10th Mar 2012 20:03
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Hello,

Depending on how AppGameKit handles OpenGL image loading ( opengl textures), i have one question :

Is a 8 bits PNG transparent image will use the same memory as a 32 bits transparent image (in AppGameKit Tier1) with mobile devices when it's loaded ? Or are your loading 8bits images as 32bits textures by default ?
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bjadams
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Posted: 10th Mar 2012 21:15
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very interesting question
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MrValentine
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Posted: 11th Mar 2012 00:37
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Interesting indeed...

As it may simply be the pixel resolution that affects the memory factor... guess we must await Lee?

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kamac
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Posted: 12th Mar 2012 12:46
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My (good i hope) guess, basing off my knowledge (which is better in DX, but it may be the same in OpenGL) is:

8bits image isn't loaded as a 32bits texture. 30 bits would be loaded as 32 bits, but not:

4 bits, 8 bits, 16 bits, 32 bits, 64 bits, 128 bits, 256 bits, 512 bits and so on, because they're multipliers of 2 or so.

Basically, loading a 8 bits texture will take less memory than loading a 32 bits texture, both with transparency.


I think I'm right, but that'd need a verify.

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Paul Johnston
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Posted: 12th Mar 2012 18:37
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Currently all images are stored as 32bit RGBA images in GPU memory. Any images that aren't a power 2 in size are scaled up to the nearest power of 2 internally on mobile devices.
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bjadams
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Posted: 12th Mar 2012 21:55
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All my graphics are 8bit!!
Could this be an optional extension to the LoadImage command in the future?
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Paul Johnston
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Posted: 12th Mar 2012 23:00
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There are formats for single channel (8 bit) greyscale, single channel alpha, or a 2 channel (16 bit) greyscale + alpha, but the smallest colour texture with alpha is the 4 channel (32 bit) RGBA.

Assuming the 1 and 2 channels textures behave with the new image manipulation commands, they are a possibility for the future.
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MikeMax
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Posted: 13th Mar 2012 05:30 Edited at: 13th Mar 2012 05:42
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For precision, in apple doc (iOS) :

(sorry the link tag doesn't work for this url lol)

http://developer.apple.com/library/ios/#documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/TechniquesForWorkingWithTextureData/TechniquesForWorkingWithTextureData.html%23//apple_ref/doc/uid/TP40008793-CH104-SW1

Quote: "If your application cannot use compressed textures, consider using a lower precision pixel format. A texture in RGB565, RGBA5551, or RGBA4444 format uses half the memory of a texture in RGBA8888 format. Use RGBA8888 only when your application needs that level of quality."


the RGBA5551 format or the RGBA4444 format could be the solution in most of cases (RGBA5551 for non-gradient transparency .. which may be sufficient if we want to make a game with a lot of contents)

It could be great to have the possibility to specify it... i'm facing memory limits for my game ... and i don't need 24 bits colors all the time ... 15 bits is often sufficient for me

So... waiting for future image manipulation commands
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bjadams
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Posted: 13th Mar 2012 09:43
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Same problem here MikeMax.
Having the option to specify either the bit depth or RGBA format with the LoadImage or CreatSprite commands would be great.
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Paul Johnston
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Posted: 13th Mar 2012 15:52
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Whilst OpenGL does support RGB565, looking at the OpenGL ES 1.1 spec for embedded devices it claims only GL_ALPHA, GL_RGB, GL_RGBA, GL_LUMINANCE, or GL_LUMINANCE_ALPHA are supported. If iOS supports it then it looks like some devices extend this spec to provide more formats, but unfortunately it isn't guaranteed to work across all devices.
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bjadams
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Posted: 13th Mar 2012 15:59
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ahhhh too bad
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