Error decode PPM about openjph HOT 7 CLOSED

Hi Lucas,

This images has two downsampled components. The only way to save them to ppm is if you interpolate these two components. Then, if you were to interpolate, where do these component sit relative to the first component (the one that is not downsampled); possible answers are: 0,0 or 1,1 or 0.5, 0.5 and many other locations.

We cannot expect a decoder to be able to do all possible imagined tasks. For these tasks, you have to write your own code.

Kind regards,
Aous

from openjph.

Hi Aous
Maybe I'm doing something wrong. What should be sampling for 4: 2: 2?
I'm just thinking. Since openjpeg allows 4: 2: 2 sampling. Maybe there's no blockage there.

Edit: I used your latest grok codecs. Previously, jp2 exif files had blotches. Now I have a mistake, but I will not upset the grok. regards
https://github.com/GrokImageCompression/grok/issues/253
ojph warning 0x00010001 at ojph_block_decoder.cpp:1020: A malformed codeblock that has more than one coding pass, but zero length for 2nd and potential 3rd pass.

[2021-09-15 09:16:31.156] [error] Error in HT block coder
[2021-09-15 09:16:31.156] [error] Failed to decompress tile 0/1
[2021-09-15 09:16:31.156] [error] Failed to decompress JP2 file

from openjph.

You setting is correct. -downsamp {1,1},{2,1},{2,1}.
When YUV is used, OpenJPH store image components as images, no color transform is employed. Also, the .j2c file tells the decoder not use color transform.

I do not know what happens in OpenJPEG; when you save to ppm, II think the result would still be in YUV, not in RGB.
Also not sure if the up-sampling is correct.

from openjph.

When YUV is used, OpenJPH store image components as images, no color transform is employed. Also, the .j2c file tells the decoder not use color transform.

OK. And it generally keeps some subsamling data. For RGB24/yuv444 I have red photos when decoding.

from openjph.

It keeps the sub-sampling data. Like you discovered, it does not perform color transform.

from openjph.

OK. Right. There is no info. I should only decode to PPM.

from openjph.

If you encode ppm, decode to ppm. If you encode yuv, decode to yuv.

from openjph.