diff options
Diffstat (limited to 'converter/other/bmptopnm.c')
| -rw-r--r-- | converter/other/bmptopnm.c | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/converter/other/bmptopnm.c b/converter/other/bmptopnm.c index 39a90aa2..dd7be892 100644 --- a/converter/other/bmptopnm.c +++ b/converter/other/bmptopnm.c @@ -42,6 +42,10 @@ struct bitPosition { Example: if 16 bits are laid out as XRRRRRGGGGGBBBBB then the shift count for the R component is 10 and the mask is 0000000000011111. + + A 'mask' of zero denotes absence of any bits; e.g. in the example + above, the mask for the transparency component is zero because there + is no transparency component . 'shift' is arbitrary in that case. */ unsigned int shift; /* How many bits right you have to shift the value to get the subject @@ -667,11 +671,15 @@ extractBitFields(unsigned int const rasterval, (rasterval >> pixelformat.blu.shift) & pixelformat.blu.mask; unsigned int const abits = (rasterval >> pixelformat.trn.shift) & pixelformat.trn.mask; - - *rP = (unsigned int) rbits * maxval / pixelformat.red.mask; - *gP = (unsigned int) gbits * maxval / pixelformat.blu.mask; - *bP = (unsigned int) bbits * maxval / pixelformat.grn.mask; - *aP = (unsigned int) abits * maxval / pixelformat.trn.mask; + + *rP = pixelformat.red.mask > 0 ? + (unsigned int) rbits * maxval / pixelformat.red.mask : 0; + *gP = pixelformat.grn.mask > 0 ? + (unsigned int) gbits * maxval / pixelformat.grn.mask : 0; + *bP = pixelformat.blu.mask > 0 ? + (unsigned int) bbits * maxval / pixelformat.blu.mask : 0; + *aP = pixelformat.trn.mask > 0 ? + (unsigned int) abits * maxval / pixelformat.trn.mask : 0; } |