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Output console warning if chrome images are abusing alpha (8-bit

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channel to represent binary alpha or fully opaque 1-bit alpha).
r=bryner, a=brendan.
This commit is contained in:
tor%cs.brown.edu 2000-09-06 04:42:38 +00:00
parent 5af614d016
commit 027dad8637
1 changed files with 61 additions and 0 deletions
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61
modules/libimg/src/if.cpp
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@ -1267,6 +1267,63 @@ il_image_abort(il_container *ic)
}
}
static void
IL_ChromeAlphaAbuseCheck(il_container *ic)
{
IL_Pixmap *mask = ic->mask;
NI_PixmapHeader *header = &mask->header;
PRUint8 *alpha = (PRUint8 *)mask->bits;
if (ic->image->header.alpha_bits == 8) {
unsigned num000 = 0, num255 = 0;
for (unsigned y=0; y<header->height; y++, alpha+=header->widthBytes)
for (unsigned x=0; x<header->width; x++) {
if (alpha[x] == 0)
num000++;
else if (alpha[x] == 255)
num255++;
}
if (num000+num255 == header->width*header->height) {
fprintf(stderr, "CHROME ALPHA ABUSE\n");
fprintf(stderr, "\tusing an 8-bit alpha channel to represent binary alpha\n");
fprintf(stderr, "\t%s\n", ic->url_address);
fprintf(stderr, "\tnum000=%d num255=%d sum=%d w*h=%d\n",
num000, num255, num000+num255, header->width*header->height);
}
} else if (ic->image->header.alpha_bits == 1) {
PRBool constAlpha=PR_TRUE;
/* check full bytes */
for (unsigned y=0;
y<header->height && constAlpha;
y++, alpha+=header->widthBytes)
for (unsigned x=0; x<header->width/8; x++)
if (alpha[x] != 255) {
constAlpha = PR_FALSE;
break;
}
/* check trailing bits */
PRUint8 mask = 255;
mask <<= 8-(header->width&7);
if (mask && constAlpha)
for (unsigned y=0;
y<header->height;
y++, alpha+=header->widthBytes)
if ((alpha[header->width/8]&mask) != mask) {
constAlpha = PR_FALSE;
break;
}
if (constAlpha) {
fprintf(stderr, "CHROME ALPHA ABUSE\n");
fprintf(stderr, "\tfully opaque 1-bit alpha mask\n");
fprintf(stderr, "\t%s\n", ic->url_address);
}
}
}
void
IL_StreamComplete(il_container *ic, PRBool is_multipart)
{
@ -1288,6 +1345,10 @@ IL_StreamComplete(il_container *ic, PRBool is_multipart)
difference, ic->url_address));
#endif /* DEBUG */
/* Check for abuse of alpha in chrome images */
if ((ic->moz_type == TYPE_CHROME) && ic->image->header.alpha_bits)
IL_ChromeAlphaAbuseCheck(ic);
ic->is_multipart = is_multipart;
if (ic->imgdec)