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stb_image: JPEG: Support 4-channel CMYK/YCCK images

pull/427/head
Jeremy Sawicki 2017-03-03 18:46:17 -08:00
parent 6f6e11f85f
commit 954cb53088
1 changed files with 75 additions and 7 deletions
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82
stb_image.h
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@ -1691,6 +1691,7 @@ typedef struct
int succ_high;
int succ_low;
int eob_run;
int app14;
int rgb;
int scan_n, order[4];
@ -2625,7 +2626,7 @@ static void stbi__jpeg_reset(stbi__jpeg *j)
j->code_bits = 0;
j->code_buffer = 0;
j->nomore = 0;
j->img_comp[0].dc_pred = j->img_comp[1].dc_pred = j->img_comp[2].dc_pred = 0;
j->img_comp[0].dc_pred = j->img_comp[1].dc_pred = j->img_comp[2].dc_pred = j->img_comp[3].dc_pred = 0;
j->marker = STBI__MARKER_none;
j->todo = j->restart_interval ? j->restart_interval : 0x7fffffff;
j->eob_run = 0;
@ -2839,11 +2840,39 @@ 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 == 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");
}
@ -2918,7 +2947,7 @@ static int stbi__process_frame_header(stbi__jpeg *z, int scan)
s->img_y = stbi__get16be(s); if (s->img_y == 0) return stbi__err("no header height", "JPEG format not supported: delayed height"); // Legal, but we don't handle it--but neither does IJG
s->img_x = stbi__get16be(s); if (s->img_x == 0) return stbi__err("0 width","Corrupt JPEG"); // JPEG requires
c = stbi__get8(s);
if (c != 3 && c != 1) return stbi__err("bad component count","Corrupt JPEG"); // JFIF requires
if (c != 3 && c != 1 && c != 4) return stbi__err("bad component count","Corrupt JPEG");
s->img_n = c;
for (i=0; i < c; ++i) {
z->img_comp[i].data = NULL;
@ -2931,7 +2960,7 @@ static int stbi__process_frame_header(stbi__jpeg *z, int scan)
for (i=0; i < s->img_n; ++i) {
static unsigned char rgb[3] = { 'R', 'G', 'B' };
z->img_comp[i].id = stbi__get8(s);
if (z->img_comp[i].id == rgb[i])
if (s->img_n == 3 && z->img_comp[i].id == rgb[i])
++z->rgb;
q = stbi__get8(s);
z->img_comp[i].h = (q >> 4); if (!z->img_comp[i].h || z->img_comp[i].h > 4) return stbi__err("bad H","Corrupt JPEG");
@ -3004,6 +3033,7 @@ 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->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");
@ -3485,7 +3515,7 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
if (!stbi__decode_jpeg_image(z)) { stbi__cleanup_jpeg(z); return NULL; }
// determine actual number of components to generate
n = req_comp ? req_comp : z->s->img_n;
n = req_comp ? req_comp : z->s->img_n >= 3 ? 3 : 1;
if (z->s->img_n == 3 && n < 3 && z->rgb != 3)
decode_n = 1;
@ -3558,6 +3588,28 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
} else {
z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x, n);
}
} else if (z->s->img_n == 4) {
if (z->app14 == 0) { // CMYK
for (i=0; i < z->s->img_x; ++i) {
stbi_uc k = coutput[3][i];
out[0] = (coutput[0][i] * k + 128) / 255;
out[1] = (coutput[1][i] * k + 128) / 255;
out[2] = (coutput[2][i] * k + 128) / 255;
out[3] = 255;
out += n;
}
} else if (z->app14 == 2) { // YCCK
z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x, n);
for (i=0; i < z->s->img_x; ++i) {
stbi_uc k = coutput[3][i];
out[0] = ((255 - out[0]) * k + 128) / 255;
out[1] = ((255 - out[1]) * k + 128) / 255;
out[2] = ((255 - out[2]) * k + 128) / 255;
out += n;
}
} else { // YCbCr + alpha? Ignore the fourth channel for now
z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x, n);
}
} else
for (i=0; i < z->s->img_x; ++i) {
out[0] = out[1] = out[2] = y[i];
@ -3575,6 +3627,22 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
out[1] = 255;
}
}
} else if (z->s->img_n == 4 && z->app14 == 0) {
for (i=0; i < z->s->img_x; ++i) {
stbi_uc k = coutput[3][i];
stbi_uc r = (coutput[0][i] * k + 128) / 255;
stbi_uc g = (coutput[1][i] * k + 128) / 255;
stbi_uc b = (coutput[2][i] * k + 128) / 255;
out[0] = stbi__compute_y(r, g, b);
out[1] = 255;
out += n;
}
} else if (z->s->img_n == 4 && z->app14 == 2) {
for (i=0; i < z->s->img_x; ++i) {
out[0] = ((255 - coutput[0][i]) * coutput[3][i] + 128) / 255;
out[1] = 255;
out += n;
}
} else {
stbi_uc *y = coutput[0];
if (n == 1)
@ -3587,7 +3655,7 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
stbi__cleanup_jpeg(z);
*out_x = z->s->img_x;
*out_y = z->s->img_y;
if (comp) *comp = z->s->img_n; // report original components, not output
if (comp) *comp = z->s->img_n >= 3 ? 3 : 1; // report original components, not output
return output;
}
}
@ -3623,7 +3691,7 @@ static int stbi__jpeg_info_raw(stbi__jpeg *j, int *x, int *y, int *comp)
}
if (x) *x = j->s->img_x;
if (y) *y = j->s->img_y;
if (comp) *comp = j->s->img_n;
if (comp) *comp = j->s->img_n >= 3 ? 3 : 1;
return 1;
}