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stb_image: JPEG: Improved detection of RGB images

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This commit is contained in:
Jeremy Sawicki 2017-03-03 16:24:21 -08:00
parent 6f6e11f85f
commit 9e76bb5108
1 changed files with 50 additions and 5 deletions
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55
stb_image.h
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@ -1691,6 +1691,8 @@ typedef struct
int succ_high;
int succ_low;
int eob_run;
int jfif;
int app14;
int rgb;
int scan_n, order[4];
@ -2839,11 +2841,50 @@ static int stbi__process_marker(stbi__jpeg *z, int m)
}
return L==0;
}
// check for comment block or APP blocks
if ((m >= 0xE0 && m <= 0xEF) || m == 0xFE) {
stbi__skip(z->s, stbi__get16be(z->s)-2);
L = stbi__get16be(z->s);
if (L < 2) {
if (m == 0xFE)
return stbi__err("bad COM len","Corrupt JPEG");
else
return stbi__err("bad APP len","Corrupt JPEG");
}
L -= 2;
if (m == 0xE0 && L >= 5) { // JFIF APP0 segment
static const unsigned char tag[5] = {'J','F','I','F','\0'};
int ok = 1;
int i;
for (i=0; i < 5; ++i)
if (stbi__get8(z->s) != tag[i])
ok = 0;
L -= 5;
if (ok) {
z->jfif = 1;
}
} else if (m == 0xEE && L >= 12) { // Adobe APP14 segment
static const unsigned char tag[6] = {'A','d','o','b','e','\0'};
int ok = 1;
int i;
for (i=0; i < 6; ++i)
if (stbi__get8(z->s) != tag[i])
ok = 0;
L -= 6;
if (ok) {
stbi__get8(z->s); // version
stbi__get16be(z->s); // flags0
stbi__get16be(z->s); // flags1
z->app14 = stbi__get8(z->s); // color transform
L -= 6;
}
}
stbi__skip(z->s, L);
return 1;
}
return stbi__err("unknown marker","Corrupt JPEG");
}
@ -3004,6 +3045,8 @@ static int stbi__process_frame_header(stbi__jpeg *z, int scan)
static int stbi__decode_jpeg_header(stbi__jpeg *z, int scan)
{
int m;
z->jfif = 0;
z->app14 = -1;
z->marker = STBI__MARKER_none; // initialize cached marker to empty
m = stbi__get_marker(z);
if (!stbi__SOI(m)) return stbi__err("no SOI","Corrupt JPEG");
@ -3475,7 +3518,7 @@ typedef struct
static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp, int req_comp)
{
int n, decode_n;
int n, decode_n, is_rgb;
z->s->img_n = 0; // make stbi__cleanup_jpeg safe
// validate req_comp
@ -3487,7 +3530,9 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
// determine actual number of components to generate
n = req_comp ? req_comp : z->s->img_n;
if (z->s->img_n == 3 && n < 3 && z->rgb != 3)
is_rgb = z->s->img_n == 3 && (z->rgb == 3 || (z->app14 == 0 && !z->jfif));
if (z->s->img_n == 3 && n < 3 && !is_rgb)
decode_n = 1;
else
decode_n = z->s->img_n;
@ -3547,7 +3592,7 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
if (n >= 3) {
stbi_uc *y = coutput[0];
if (z->s->img_n == 3) {
if (z->rgb == 3) {
if (is_rgb) {
for (i=0; i < z->s->img_x; ++i) {
out[0] = y[i];
out[1] = coutput[1][i];
@ -3565,7 +3610,7 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
out += n;
}
} else {
if (z->rgb == 3) {
if (is_rgb) {
if (n == 1)
for (i=0; i < z->s->img_x; ++i)
*out++ = stbi__compute_y(coutput[0][i], coutput[1][i], coutput[2][i]);