[FFmpeg-devel] [PATCH] lavfi: add xbr filter

[Clément Bœsch]

On Sun, Oct 26, 2014 at 02:51:48PM +0530, arwa arif wrote:
[...]
> +/**
> +* Mixes a pixel A, with pixel B, with B's transperancy set to 'a'
> +* In other words, A is a solid color (bottom) and B is a transparent color (top)
> +**/
> +static int mix(AVFrame *in,int x1,int y1,int x2,int y2,int a,int mode){

> +    /*If red color*/
> +    int col1,col2;
> +    if(mode==0){
> +        col1 = *(in->data[0] + y1 * in->linesize[0] + x1*3);
> +        col2 = *(in->data[0] + y2 * in->linesize[0] + x2*3);
> +    }
> +
> +    /*If green color*/
> +    else if(mode==1){
> +        col1 = *(in->data[0] + y1 * in->linesize[0] + x1*3 + 1);
> +        col2 = *(in->data[0] + y2 * in->linesize[0] + x2*3 + 1);
> +    }
> +
> +    /*If blue color*/
> +    else{
> +        col1 = *(in->data[0] + y1 * in->linesize[0] + x1*3 + 2);
> +        col2 = *(in->data[0] + y2 * in->linesize[0] + x2*3 + 2);
> +    }

All of this can be probably be simplified to:

  const int col1 = in->data[0][y1 * in->linesize[0] + x1*3 + mode];
  const int col2 = in->data[0][y2 * in->linesize[0] + x2*3 + mode];

And "mode" is badly named, "layer", "color" or "channel" would be more
appropriate.

[...]
> +/**
> +* Applies the xBR filter rules.
> +**/
> +static void apply_edge_detection_rules(AVFrame *in,AVFrame *out,int x,int y){
> +
> +    /* Matrix: (10 is 0,0 i.e: current pixel)
> +    -2 | -1| 0| +1| +2 (x)
> +    ______________________________
> +    -2 | [ 0][ 1][ 2]
> +    -1 | [ 3][ 4][ 5][ 6][ 7]
> +     0 | [ 8][ 9][10][11][12]
> +    +1 | [13][14][15][16][17]
> +    +2 | [18][19][20]
> +    |(y)|

Why are the spaces totally broken here?

Unless I'm mistaken, you want this:

          -2 | -1| 0| +1| +2
       +---------------------->  (x)
    -2 |     [ 0][ 1][ 2]
    -1 | [ 3][ 4][ 5][ 6][ 7]
     0 | [ 8][ 9][10][11][12]
    +1 | [13][14][15][16][17]
    +2 |     [18][19][20]
       |
  (y)  v

And then my question becomes: why don't you pick the original naming with
the letters as in the specs?

[...]

-- 
Clément B.
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