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To reconstruct each compressed 4-pixel by 4-pixel block, the 16-bit luminance bitmap is consulted for each block. Depending on whether an element of the bitmap is 1 or 0, one of the two 8-bit indices into the lookup table is selected and then dereferenced and the corresponding 24-bit per pixel color value is retrieved. [1] [2] [3]
[1] [2] [3] Modern standards tend to use bits per component, [1] [2] [4] [5] but historical lower-depth systems used bits per pixel more often. Color depth is only one aspect of color representation, expressing the precision with which the amount of each primary can be expressed; the other aspect is how broad a range of colors can be expressed ...
On grayscale images, a minimum of 6.5 bits per pixel is enough (a comparable Q=100 quality color information requires about 25% more encoded bits). The highest quality image below (Q=100) is encoded at nine bits per color pixel, the medium quality image (Q=25) uses one bit per color pixel.
The size of raster image files is positively correlated with the number of pixels in the image and the color depth (bits per pixel). Images can be compressed in various ways, however. A compression algorithm stores either an exact representation or an approximation of the original image in a smaller number of bytes that can be expanded back to ...
The 8-bit per pixel (8bpp) format supports 256 distinct colors and stores 1 pixel per 1 byte. Each byte is an index into a table of up to 256 colors. The 16-bit per pixel (16bpp) format supports 65536 distinct colors and stores 1 pixel per 2-byte WORD. Each WORD can define the alpha, red, green and blue samples of the pixel.
The DSC standard supports up to a 3∶1 compression ratio (reducing the data stream to 8 bits per pixel) with constant or variable bit rate, RGB or Y′C B C R 4:4:4, 4:2:2, or 4:2:0 color format, and color depth of 6, 8, 10, or 12 bits per color component.
The original 'ETC1' compression scheme provides 6x compression of 24-bit RGB data. It does not support the compression of images with Alpha components, although there are work-arounds for this. [3] ETC1 takes 4x4 groups of pixel data and compresses each into a single 64-bit word. The 4×4 pixel group is first divided into two 4×2 chunks ...
All convert a 4×4 block of pixels to a 64-bit or 128-bit quantity, resulting in compression ratios of 6:1 with 24-bit RGB input data or 4:1 with 32-bit RGBA input data. S3TC is a lossy compression algorithm, resulting in image quality degradation, an effect which is minimized by the ability to increase texture resolutions while maintaining the ...