Convert YUV to lossy compression with OpenCV

Question

How would I go about converting an image in YUV colorspace to a JPEG image?

I have a raw image data saved in a char* variable:

char* frame = (char*)camera->getFrame(); // YUV colorspace image data

I need to convert this to a JPEG image data instead. I don't want to save it to disk because I will be sending it in a stream.

score 1 · Accepted Answer · edited May 23 '17 at 12:29

1

OpenCV itself does not export this functionality. Cleanest is to use libjpeg for encoding. See the answers to these questions:

edited May 23 '17 at 12:29

Community

answered Nov 18 '10 at 15:16

ypnos

Well, that's not good. I need to compress images before streaming them on a system with closed embedded linux. It only has OpenCV and I cannot install any additional libraries. Is there some other way how to compress images before streaming them so they are lighter in size? I need to save badwidth. Is using gzip a good idea? – Richard Knop Nov 18 '10 at 20:13
In the accepted answer of my second link, you will find that OpenCV internally has functions for encoding to JPEG without writing to a file. It is just that in newer versions of OpenCV they might change without further notice, as they are not part of the API. If you're stuck on a closed system with specific library setting, you may not care for that anyway. Furthermore, the zip algorithm will always be helpful but you should not expect a reduction of more than 50% with it.. – ypnos Nov 18 '10 at 22:35

score 1 · Answer 2 · answered Nov 19 '10 at 09:42

Check the opencv src for the file cvcolor.cpp. This has all the color conversions in it.

I suggest you modify the existing routines near this line:

/* BGR/RGB -> YCrCb */

They are almost exactly what you need for YUV encoding. if its 4:4:4 and not 4:2:2 or 4:1:1

for jpg compression

The jpg encoder and decoder are in grfmt_jpeg.cpp which happens to #include "jpeglib.h"
You can call these directly

2 Answers2