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plug-ins: fix #10240 DDS saved as RGB10A2 loads incorrectly 

There were 2 issues here:
1. When more than 8 bits per sample are used, a previous commit changed
it so that we would be using 16-bit integer mode instead of 8-bit.
However, the actual code for this specific format was not updated to
reflect that.
We fix this by computing 16-bits per channel values and upshifting the
10 and 2-bit samples to 16 bit per channel.

2. The computation of masks was incorrect. It computed each channel
mask separately, based on whether it was <= 8 or not.
However, if any channel needs more than 8 bits, all masks should be
computed 16 bits since we will then 16-bit integer mode.
We fix this by checking all channel bits together, and if any is higher
than 8, but not more than 16,  we use 16-bit masks.
I also took this opportunity to add support for 32-bit masks if we
ever need those.
This commit is contained in:
Jacob Boerema 2023-11-01 15:24:02 -04:00
parent e3b2f40ac2
commit 74adec7656
1 changed files with 32 additions and 19 deletions
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51
plug-ins/file-dds/ddsread.c
View File

@ -227,22 +227,31 @@ read_dds (GFile *file,
d.gbits = color_bits (hdr.pixelfmt.gmask);
d.bbits = color_bits (hdr.pixelfmt.bmask);
d.abits = color_bits (hdr.pixelfmt.amask);
if (d.rbits <= 8)
d.rmask = (hdr.pixelfmt.rmask >> d.rshift) << (8 - d.rbits);
if (d.rbits <= 8 && d.gbits <= 8 && d.bbits <= 8 && d.abits <= 8)
{
/* 8 bits per sample */
d.rmask = (hdr.pixelfmt.rmask >> d.rshift) << (8 - d.rbits);
d.gmask = (hdr.pixelfmt.gmask >> d.gshift) << (8 - d.gbits);
d.bmask = (hdr.pixelfmt.bmask >> d.bshift) << (8 - d.bbits);
d.amask = (hdr.pixelfmt.amask >> d.ashift) << (8 - d.abits);
}
else if (d.rbits <= 16 && d.gbits <= 16 && d.bbits <= 16 && d.abits <= 16)
{
/* 16 bits per sample */
d.rmask = (hdr.pixelfmt.rmask >> d.rshift) << (16 - d.rbits);
d.gmask = (hdr.pixelfmt.gmask >> d.gshift) << (16 - d.gbits);
d.bmask = (hdr.pixelfmt.bmask >> d.bshift) << (16 - d.bbits);
d.amask = (hdr.pixelfmt.amask >> d.ashift) << (16 - d.abits);
}
else
d.rmask = (hdr.pixelfmt.rmask >> d.rshift) << (16 - d.rbits);
if (d.gbits <= 8)
d.gmask = (hdr.pixelfmt.gmask >> d.gshift) << (8 - d.gbits);
else
d.gmask = (hdr.pixelfmt.gmask >> d.gshift) << (16 - d.gbits);
if (d.bbits <= 8)
d.bmask = (hdr.pixelfmt.bmask >> d.bshift) << (8 - d.bbits);
else
d.bmask = (hdr.pixelfmt.bmask >> d.bshift) << (16 - d.bbits);
if (d.abits <= 8)
d.amask = (hdr.pixelfmt.amask >> d.ashift) << (8 - d.abits);
else
d.amask = (hdr.pixelfmt.amask >> d.ashift) << (16 - d.abits);
{
/* 32 bits per sample in case we need this in the future */
d.rmask = (hdr.pixelfmt.rmask >> d.rshift) << (32 - d.rbits);
d.gmask = (hdr.pixelfmt.gmask >> d.gshift) << (32 - d.gbits);
d.bmask = (hdr.pixelfmt.bmask >> d.bshift) << (32 - d.bbits);
d.amask = (hdr.pixelfmt.amask >> d.ashift) << (32 - d.abits);
}
d.gimp_bps = 1; /* Most formats will be converted to 1 byte per sample */
if (hdr.pixelfmt.flags & DDPF_FOURCC)
@ -1230,11 +1239,15 @@ load_layer (FILE *fp,
{
if (hdr->pixelfmt.amask == 0xc0000000) /* handle RGB10A2 */
{
pixels[pos + ired] = (pixel >> d->rshift) >> 2;
pixels[pos + 1] = (pixel >> d->gshift) >> 2;
pixels[pos + iblue] = (pixel >> d->bshift) >> 2;
guint16 *pixels16 = (guint16 *) &pixels[pos];
pixels16[ired] = (guint16) (pixel >> d->rshift << (16 - d->rbits));
pixels16[1] = (guint16) (pixel >> d->gshift << (16 - d->gbits));
pixels16[iblue] = (guint16) (pixel >> d->bshift << (16 - d->bbits));
if (hdr->pixelfmt.flags & DDPF_ALPHAPIXELS)
pixels[pos + 3] = (pixel >> d->ashift << (8 - d->abits) & d->amask) * 255 / d->amask;
{
pixels16[3] = (guint16) ((pixel >> d->ashift << (16 - d->abits) & d->amask) * 65535 / d->amask);
}
}
else if (d->rmask > 0 && d->gmask > 0 && d->bmask > 0)
{