I´m trying to implement a Sobel algorithm for edge-detection for a YUV camera stream. Initially it seems quite easy but I´m not sure if this approach is correct:
The black and white image works perfectly and I can see it on the PC application which I wrote, but when I´m applying the Sobel filter to Y component I´m getting this:
the code:
#define index(xx, yy) ((yy * width + xx) * 2) & 0xFFFFFFFE // address multiple of 2
(...............)
for (y=1, y < height-1; y++){
for (x=1, y < width-1; y++){
pixel_valueY_h=0.0;
pixel_valueY_v=0.0;
for (j= -1; j<2; j++){
for (i= -1; i<2; i++){
offset= index(x+1, y+1);
pixel_valueY_h += (sobel_h[j + 1][i + 1])* input[offset+1]; //offset+1=> Y component
pixel_valueY_v += (sobel_v[j + 1][i + 1])* input[offset+1];
}
}
offset = index(x,y);
pixel_value= sqrt1((pixel_valueY_h * pixel_valueY_h)+(pixel_valueY_v * pixel_valueY_v));
if (pixel_value > 255) pixel_value=255;
if (pixel_value < 0) pixel_value=0;
//output frame
output[offset] &=0x00; //U and V components = 0
output[offset+1] &=(255- (unsigned char)pixel_value );
}
}
(...............)
Any clue about what is happening? Thanks in advance.
Finally I've got it working, the problem was the memory addressing using the macro: #define index(xx, yy) ((yy * width + xx) * 2) & 0xFFFFFFFE which for some reason was giving incorrect addresses. Instead I added the line ( ((yy * width + xx) * 2) & 0xFFFFFFFE) in the code and like that (without modifications) is working perfectly.
Thanks.
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