jpeg recompression

jpeg recompression

hi, im owner of ipp 4 for linux, and i need simple sample for this:

i have jpeg image in memory in buffer data with size 50000 bytes. i need recompress it to 50% quality jpeg and put it to buffer2.

how can i do it?

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Hi,

you need to decompress your JPEG to intermediate buffer and after that you can compress it with any desired compression ratio.

There is some performance trick. You can decompress only DCT coefficients, dequantize them, after that you can requantize them with new quality setting and compress with huffman function. Right now we have no such sample in IPP, but if you are familiar enough with JPEG technology it is not complicated task to write such code yourself (or modify our existing IPP sample).

Regards,
Vladimir

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