2007.04.11 13:26 "Re: [Tiff] DC to tiff", by Joris Van Damme

Anybody know how to print a DC to a tiff file? I can't seem to make it

for(UINT32 row = 0; row < height; row++ ){

// initialize the scan line to zero

memset(pdst,0,(size_t)(width * 3));

// moving the data from the dib to a row structure that

// can be used by the tiff library

for(UINT32 col = 0; col < (UINT32)width; col++){

src_index=(width-row-1)*width*bytecount+col*bytecount;

dst_index = col*3;

pdst[dst_index++]=psrc[src_index+2];

pdst[dst_index++]=psrc[src_index+1];

pdst[dst_index]=psrc[src_index];

}

There may be other problems with your code, I've not looked at it too carefully, but the src_index calculation is very suspicious. 'row' loops from 0 to height-1, so any calculation of width-row is nonsense, is, like, three cows minus two horses (but maybe with a lot more progress in the field of genetic manipulation before the latter will start making sense in the end ;-)). You probably mean height-row-1, as you're reading from bottom-up dibs. But even then, the calculation isn't correct, as DIB scanlines are padded to multiple of 32bits. And even then, the placement of that calculation inside that inner RGB channel swapping loop is far from ideal...

How about replacing the above code snippet with...

UINT8* src_pos;
UINT8* dst_pos;

for(UINT32 row = 0; row < height; row++ ){
    // initialize the scan line to zero
    memset(pdst,0,(size_t)(width * 3));
    // moving the data from the dib to a row structure that
    // can be used by the tiff library
    src_pos=(UINT8*)psrc+(((height-row-1)*width*3+3)&(~3));
    dst_pos=(UINT8*)pdst;
    for(UINT32 col = 0; col < (UINT32)width; col++){
        dst_pos[0]=src_pos[2];
        dst_pos[1]=src_pos[1];
        dst_pos[2]=src_pos[0];
        src_pos+=3;
        dst_pos+=3;
    }

That will work if the DIB is 24bits per pixel, as seems to be the case. If you want more flexible code that works for other DIB bitdepths, the best is to adapt the above snippet for other DIB bitdepths, and select outside of the inner RGB channel swapping loop.

Best regards,

Joris Van Damme
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