CODEWITHSUNDEEP
c
kavya
kavya

Reputation: 21

conversion from rgb to yuv 4:2:0

how do i make a 160*70 bitmap image move over a 640*280 bitmap image and reflect off its edge after converting both bitmap images into yuv 4:4:4and write it into a single yuv file ? and how do i convert the same into yuv 4:2:0?could you please help me out as to how do i code the same in c?

Upvotes: 2

Views: 7123

Answers (2)

Jacob
Jacob

Reputation: 34601

This wikipedia article has RGB -> YUV440.

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And RGB -> YUV420 is described in the same article in this section.

I did not understand:

how do i make a 160*70 bitmap image move over a 640*280 bitmap image and reflect off its edge

Upvotes: 1

R.. GitHub STOP HELPING ICE
R.. GitHub STOP HELPING ICE

Reputation: 215193

Converting to YUV 4:4:4 - This is purely an affine transformation on each RGB vector. Just use the proper formula for whichever YUV variant you need. You'll probably want to separate the image into planes at this point too.

Converting to YUV 4:2:0 - This is purely a resampling problem. You need to resample the U and V planes to half width and half height. Do NOT just skip samples ("nearest-neighbor sampling"); this will result in very ugly aliasing. You could simply average the corresponding 2x2 squares or use a more advanced filter. For downsampling, area-average is pretty close to ideal anyway; gaussian may give mildly better results.

If you don't mind using library code, libswscale from ffmpeg can do both of these steps for you, and will do it very fast.

Finally, moving the small image across the big one: Is it purely a rectangular image or does it use an alpha channel? Either way you'll simply need to loop over the coordinates you want it to appear at and output an image for each point. If it's rectangular you just then copy pixels, whereas if it has an alpha channel you need to use that for alpha blending (interpolating between the pixel values according to the alpha value).

Upvotes: 4

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