Friday, August 28, 2009

jpeg compression

Hey John,

I'm working on a project for -- that closely relates to the jpeg decompression stuff you showed me a while ago and was wondering if you could help me out...this time I am trying to compress a bitmap into a jpeg using the same IJG library. I've got the library working for the most part, except that something strange seems to be going on with the colors in some instances. Attached is a bitmap and the associated compressed jpeg. As you can see, a lot of the yellows in the bitmap turn to blues in the jpeg. Do you have any idea what I am doing wrong? In nature scenes, it is a lot less noticeable.

I should note that the bitmap started out 32 bit, and I had to convert it to 24 bit before feeding it to the compression engine. So, do you have any ideas?


What are your inputs and storage format?

it looks like your colors are crossed, I recommend getting a red, green and blue object (and yellow) so you can compair and see exactly what colors gone wrong.

Could be U/V or R/B reversal.


Input is RGB. I'll give that a shot. Thanks.

You were correct sir. RB reversal. Thanks again!


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