ImageProcessing-ElectronicPublications/jpge

mask file

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zvezdochiot commented

Hi @trufanov-nok and @plzombie .

Собственно, jpeg кодер. Возникла задача дополнительной фильтрации по маске. Саму задачу изложил здесь: wfus/jpeg-compressor@839ca29#commitcomment-120504770 . Продублирую:

This encoder is specific and ideal for comic book material. It is more suitable for such material than mozjpeg (IMHO).

For certain purposes (https://github.com/ImageProcessing-ElectronicPublications/imthreshold/blob/master/bash/pdf/mfbpdf-jbig2jpge.sh), I would like to have an additional optional quantizer in this encoder, set by the mask file:

jpge [options] <source_file> <dest_file> <quality_factor> [mask_file]

Where for each 8x8 block mask_file, the average brightness value is calculated: qmask=sum(area8x8)/count(area8x8). And with the help of these values, additional filtering is performed:

/* DCT = qmask_back(qmask_forward(DCT)) */
DCT[blokid][i][j] = (int) (DCT[blockid][i][j] * (qmask[blockid] + 1) / 256); // forward
DCT[blokid][i][j] = (int) (DCT[blockid][i][j] * 256 / (qmask[blockid] + 1)); // back

Сам явно не потяну. Или потяну, но не сейчас и криво.

Буду рад любой помощи. Не буду ни капли не против приглашения людей "со стороны".

См. также ImageProcessing-ElectronicPublications/jpegquant@287610c