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selaux / node-sprite-generator

Generates image sprites and their spritesheets (css, stylus, sass or less) from sets of images. Supports retina sprites. Provides express middleware and grunt task.
MIT License
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Change compression to 0-100, update docs. #12

Closed wshaver closed 10 years ago

wshaver commented 10 years ago

There is a difference in file size between compression of 99 and 100. The current code sets an int of '9' to a compression of 99, and other ints to always end in a 9.

For example I have a generated file with these sizes: compression level : file size 50: 133kb 89: 156kb 90: 118kb 99: 155kb 100: 118kb 119: 155kb

Frankly I have no idea why the compressor has much bigger files when you give it an option that ends in in '9'. But the current way the compression options are passed to the compression forces them to end in a 9.

wshaver commented 10 years ago

Note: this is with the 'gm' compositor.

selaux commented 10 years ago

Yes there is a compression difference. The thing is that the quality parameter for graphicsmagick consists of two parts when creating a png file.

The first is the png-compression-level which is calculated as min(quality/10,9) The second is the filter method which is taken from quality % 10

With my configuration the file size gets smaller when specifying a filter of 9 (which is translated to PNG_ALL_FILTERS in graphicsmagick), but it seems different in you case. Nevertheless, i'd rather fix this by specifying a separate filter parameter to keep the api the same between all compositors. I already prepared a pull request exactly for that case here, but I still need to wait for my pull request to node-canvas to be merged, because the filter parameter in node-canvas is broken otherwise.

Sorry, no merge, but thanks anyways for the pull request :beer: