JPNG

hh hh at hyperhh.de
Thu Aug 10 19:56:20 EDT 2017


JPNG (named using JPEG and PNG) is not an image format but a compression method.
We use the file ending ".lcjpng" for that.

It takes features from both JPEG (setting JPEGquality to compress the imageData
and from the PNG compression the alphaData/transparency). It saves the alphaData,
optionally the maskData, and the JPEG-compressed imageData in one file. The
JPNG-compressed image has here, using a JPEGquality of 80, around 25% of the
PNG-compressed size.

So this may be interesting for people who wish to compress (significantly in
size) the PNG-images containing transparency in their stack/standalone and
decompress only some images for "current" use.

Compression/Decompression is very fast. 

See stack "JPNG" via the "Sample stacks" of the LC toolbar or (slower) here:
http://livecodeshare.runrev.com/stack/841/JPNG
This sample stack compresses to files or to (numbered) custom properties.

Note: I don't use the JPNG data structure of js or objC, but you can easily
convert it to that.





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