On 2012/06/17, at 1:32 AM, Stephen Swaney wrote: >> Pngs should be crushed, a lot. >> >> Preferably before being committed. > > Actually, they should not. This way we have the original > textures in the repo in case they need further work.
Anyone who actually thinks this should read http://optipng.sourceforge.net/pngtech/optipng.html particularly the following excerpt: > A lossless transform of a PNG image file is a transform which fully > preserves the rendered RGB triples (the RGB triples that come either > directly, or from a palette index, or from a gray->RGB expansion), the > rendered transparency (the alpha samples that come either directly, or from a > tRNS chunk, or the implicit 100% opacity assumed due to the lack of any > explicit transparency information), the order of rendering (sequential or > interlaced), and the semantics contained by the ancillary chunks. > This definition allows the execution of the above-mentioned image reduction > operations, and the recompression of IDAT. It also allows the alteration or > the elimination of other pieces of information that are technically valid, > but have no influence on any presentation of the image pixels: > The information that pertains to Deflate streams, either inside IDAT, or in > other compressed chunks like zTXt, iTXt or iCCP; e.g. the LZ77 window size, > the type and size of Deflate blocks, etc. (The only thing that matters is > that the decompressed byte sequence must remain the same.) > The order of palette entries inside a PLTE chunk. (When changing this order, > the information that depends on it, such as the palette-encoded pixels or the > tRNS information, must be updated accordingly.) > RGB triples that do not correspond to any pixel in the actual image, but are > stored in a tRNS chunk. > Fully opaque tRNS entries in a palette image. > Gamma correction (gAMA) or significant bit (sBIT) information inside an image > that consists exclusively of samples whose intensity is either minimum (0) or > maximum (2^bitdepth-1). > The fact that a textual comment is stored uncompressed in a tEXt chunk, or > compressed in a zTXt chunk, or with no translation in an iTXt chunk. The only sort of operations that I would define as "crushing" are those that meet the preceding definition of losslessness. -------------------------------------------------------------------------- My Web Sites: http://dak180.users.sourceforge.net/
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