eric e. dolecki

Interactive Technologist and Designer

[per riq] Since cosos2d v0.7.3, you can specify the texture's pixel format of your PNG/TIFF/BMP/GIF images.
The texture's pixel format is the way the image is stored in GPU memory.

Possible pixel formats:

• RGBA8888 (32-bit) (kTexture2DPixelFormat_RGBA8888)
• RGBA4444 (16-bit) (kTexture2DPixelFormat_RGBA4444)
• RGB5_A1 (16-bit)(kTexture2DPixelFormat_RGB5A1)
• RGB565 (16-bit) (kTexture2DPixelFormat_RGB565)

RGBA8888:

• 8 bits are assigned to the red channel, 8 bits to the green channel, 8 bits to the blue channel and 8 bits to the alpha channel.
• Use this pixel format when you need the maximum possible quality for your image.
• But it will consume the double of memory compared to 16-bit textures. Memory is a precious resource on the iPhone
• Usually it is also slower to render.
• Useful for: background image of your intro scene, and for images with lots of gradient colors

RGBA4444:

• 4 bits are assigned to the red channel, 4 bits to the green channel, 4 bits to the blue channel, and 4 bits to the alpha channel
• It gives you good quality in all channels, good speed, good memory consumption.
• Useful for: sprites that have different values of transparency

RGB5A1:

• 5 bits are assigned to the red channel, 5 bits to the green channel, 5 bits to the blue channel, and only 1 bit to the alpha channel
• It gives you good quality in RGB channels but poor quality on the A channel. It also gives you good speed and good memory consumption.
• Useful for: sprites that have transparent parts, but the transparency is either On or Off

RGB565:

• 5 bits are assigned to the red channel, 6 bits to the green channel, and 5 bits to the blue channel. It has no alpha channel support
• It gives you the best possible quality for 16-bit textures, but without alpha channel support.
• Useful for: background images in your game.

The default pixel format in v0.7.3 is RGBA8888.

How to use it:

// Set the pixel format before loading the image
// RGBA 8888 image (32-bit)
[Texture2D setDefaultAlphaPixelFormat:kTexture2DPixelFormat_RGBA8888];
Sprite *sprite1 = [Sprite spriteWithFile:@"test-rgba1.png"];

// Set the pixel format before loading the image
// RGBA 4444 image (16-bit)
[Texture2D setDefaultAlphaPixelFormat:kTexture2DPixelFormat_RGBA4444];
Sprite *sprite2 = [Sprite spriteWithFile:@"test-rgba2.png"];

// Set the pixel format before loading the image
// RGB5A1 image (16-bit)
[Texture2D setDefaultAlphaPixelFormat:kTexture2DPixelFormat_RGB5A1];
Sprite *sprite3 = [Sprite spriteWithFile:@"test-rgba3.png"];

// Set the pixel format before loading the image
// RGB565 image (16-bit)
[Texture2D setDefaultAlphaPixelFormat:kTexture2DPixelFormat_RGB565];
Sprite *sprite4 = [Sprite spriteWithFile:@"test-rgba4.png"];

// restore the default pixel format
[Texture2D setDefaultAlphaPixelFormat:kTexture2DPixelFormat_Default];

Labels: cocos2d, iPhone, pixel format