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Unpack 1/2/4 bpp into 8 bpp scanline buffer + support grayscale 1/2/4 bpp

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master
ocornut ago%!(EXTRA string=11 years)
parent f2b3ebd470
commit 3b3e2996e7
1 changed files with 88 additions and 60 deletions
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  1. 148
      stb_image.h

148
stb_image.h
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@ -63,7 +63,7 @@
James "moose2000" Brown (iPhone PNG) David Woo
Ben "Disch" Wenger (io callbacks) Roy Eltham
Martin "SpartanJ" Golini Luke Graham
Omar Cornut (1/2/4-bit palettized PNG) Thomas Ruf
Omar Cornut (1/2/4-bit png) Thomas Ruf
John Bartholomew
Optimizations & bugfixes Ken Hamada
Fabian "ryg" Giesen Cort Stratton
@ -2487,17 +2487,14 @@ static int stbi__paeth(int a, int b, int c)
#define STBI__BYTECAST(x) ((stbi_uc) ((x) & 255)) // truncate int to byte without warnings
// create the png data from post-deflated data
static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 raw_len, int out_n, stbi__uint32 x, stbi__uint32 y, int depth)
static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 raw_len, int out_n, stbi__uint32 x, stbi__uint32 y, int depth, int color)
{
stbi__context *s = a->s;
stbi__uint32 i,j,stride = x*out_n;
stbi__uint32 img_len;
int k;
int img_n = s->img_n; // copy it into a local for later
int addr_shift;
unsigned int pixel_data_shift_addr_mask;
unsigned int pixel_data_shift_addr_lshift;
stbi_uc pixel_data_mask;
stbi_uc* line8 = NULL; // point into raw when depth==8 else temporary local buffer
STBI_ASSERT(out_n == s->img_n || out_n == s->img_n+1);
a->out = (stbi_uc *) stbi__malloc(x * y * out_n);
@ -2513,89 +2510,125 @@ static int stbi__create_png_image_raw(stbi__png *a, stbi_uc *raw, stbi__uint32 r
if (raw_len < img_len) return stbi__err("not enough pixels","Corrupt PNG");
}
switch (depth)
{
case 8: addr_shift = 0; pixel_data_shift_addr_mask = 0x00; pixel_data_shift_addr_lshift = 0; pixel_data_mask = 0xFF; break;
case 4: addr_shift = 1; pixel_data_shift_addr_mask = 0x01; pixel_data_shift_addr_lshift = 2; pixel_data_mask = 0x0F; break;
case 2: addr_shift = 2; pixel_data_shift_addr_mask = 0x03; pixel_data_shift_addr_lshift = 1; pixel_data_mask = 0x03; break;
case 1: addr_shift = 3; pixel_data_shift_addr_mask = 0x07; pixel_data_shift_addr_lshift = 0; pixel_data_mask = 0x01; break;
if (depth != 8) {
line8 = (stbi_uc *) stbi__malloc((x+3) * out_n); // allocate buffer for one scanline
if (!line8) return stbi__err("outofmem", "Out of memory");
}
for (j=0; j < y; ++j) {
stbi_uc *in;
stbi_uc *cur = a->out + stride*j;
stbi_uc *prior = cur - stride;
int filter = *raw++;
if (filter > 4) return stbi__err("invalid filter","Corrupt PNG");
if (filter > 4) {
if (depth != 8) free(line8);
return stbi__err("invalid filter","Corrupt PNG");
}
if (depth == 8) {
in = raw;
raw += x*img_n;
}
else {
// unpack 1/2/4-bit into a 8-bit buffer. allows us to keep the common 8-bit path optimal at minimal cost for 1/2/4-bit
// png guarante byte alignment, if width is not multiple of 8/4/2 we'll decode dummy trailing data that will be skipped in the later loop
in = line8;
stbi_uc* decode_in = raw;
stbi_uc* decode_out = line8;
stbi_uc scale = (color == 0) ? 0xFF/((1<<depth)-1) : 1; // scale grayscale values to 0..255 range
if (depth == 4) {
for (i=x*img_n; i >= 1; i-=2, decode_in++) {
*decode_out++ = scale * ((*decode_in >> 4) );
*decode_out++ = scale * ((*decode_in ) & 0x0f);
}
raw+=(x*img_n+1)>>1;
} else if (depth == 2) {
for (i=x*img_n; i >= 1; i-=4, decode_in++) {
*decode_out++ = scale * ((*decode_in >> 6) );
*decode_out++ = scale * ((*decode_in >> 4) & 0x03);
*decode_out++ = scale * ((*decode_in >> 2) & 0x03);
*decode_out++ = scale * ((*decode_in ) & 0x03);
}
raw+=(x*img_n+3)>>2;
} else if (depth == 1) {
for (i=x*img_n; i >= 1; i-=8, decode_in++) {
*decode_out++ = scale * ((*decode_in >> 7) );
*decode_out++ = scale * ((*decode_in >> 6) & 0x01);
*decode_out++ = scale * ((*decode_in >> 5) & 0x01);
*decode_out++ = scale * ((*decode_in >> 4) & 0x01);
*decode_out++ = scale * ((*decode_in >> 3) & 0x01);
*decode_out++ = scale * ((*decode_in >> 2) & 0x01);
*decode_out++ = scale * ((*decode_in >> 1) & 0x01);
*decode_out++ = scale * ((*decode_in ) & 0x01);
}
raw+=(x*img_n+7)>>3;
}
}
// if first row, use special filter that doesn't sample previous row
if (j == 0) filter = first_row_filter[filter];
// Expanding the macro for reference (probably worth inlining the whole loop or at least splitting 8 vs 1/2/4)
// - Depth 8 (((ARR[K ])
// - Depth 4 (((ARR[K >> 1]) >> ((k & 0x01) << 2)) & 0x0F)
// - Depth 2 (((ARR[K >> 2]) >> ((k & 0x03) << 1)) & 0x03)
// - Depth 1 (((ARR[K >> 3]) >> ((k & 0x07) ) & 0x01)
#define PIXEL(ARR,K) (((ARR[(K) >> addr_shift]) >> (((7-K) & pixel_data_shift_addr_mask) << pixel_data_shift_addr_lshift)) & pixel_data_mask)
// handle first pixel explicitly
int rawk=0;
for (k=0; k < img_n; ++k, ++rawk) {
for (k=0; k < img_n; ++k) {
switch (filter) {
case STBI__F_none : cur[k] = PIXEL(raw,rawk); break;
case STBI__F_sub : cur[k] = PIXEL(raw,rawk); break;
case STBI__F_up : cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + prior[k]); break;
case STBI__F_avg : cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + (prior[k]>>1)); break;
case STBI__F_paeth : cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + stbi__paeth(0,prior[k],0)); break;
case STBI__F_avg_first : cur[k] = PIXEL(raw,rawk); break;
case STBI__F_paeth_first: cur[k] = PIXEL(raw,rawk); break;
case STBI__F_none : cur[k] = in[k]; break;
case STBI__F_sub : cur[k] = in[k]; break;
case STBI__F_up : cur[k] = STBI__BYTECAST(in[k] + prior[k]); break;
case STBI__F_avg : cur[k] = STBI__BYTECAST(in[k] + (prior[k]>>1)); break;
case STBI__F_paeth : cur[k] = STBI__BYTECAST(in[k] + stbi__paeth(0,prior[k],0)); break;
case STBI__F_avg_first : cur[k] = in[k]; break;
case STBI__F_paeth_first: cur[k] = in[k]; break;
}
}
if (img_n != out_n) cur[img_n] = 255;
in += img_n;
cur += out_n;
prior += out_n;
// this is a little gross, so that we don't switch per-pixel or per-component
if (img_n == out_n) {
#define CASE(f) \
case f: \
for (i=x-1; i >= 1; --i, cur+=img_n,prior+=img_n) \
for (k=0; k < img_n; ++k, ++rawk)
for (i=x-1; i >= 1; --i, in+=img_n,cur+=img_n,prior+=img_n) \
for (k=0; k < img_n; ++k)
switch (filter) {
CASE(STBI__F_none) cur[k] = PIXEL(raw,rawk); break;
CASE(STBI__F_sub) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + cur[k-img_n]); break;
CASE(STBI__F_up) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + prior[k]); break;
CASE(STBI__F_avg) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + ((prior[k] + cur[k-img_n])>>1)); break;
CASE(STBI__F_paeth) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + stbi__paeth(cur[k-img_n],prior[k],prior[k-img_n])); break;
CASE(STBI__F_avg_first) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + (cur[k-img_n] >> 1)); break;
CASE(STBI__F_paeth_first) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + stbi__paeth(cur[k-img_n],0,0)); break;
CASE(STBI__F_none) cur[k] = in[k]; break;
CASE(STBI__F_sub) cur[k] = STBI__BYTECAST(in[k] + cur[k-img_n]); break;
CASE(STBI__F_up) cur[k] = STBI__BYTECAST(in[k] + prior[k]); break;
CASE(STBI__F_avg) cur[k] = STBI__BYTECAST(in[k] + ((prior[k] + cur[k-img_n])>>1)); break;
CASE(STBI__F_paeth) cur[k] = STBI__BYTECAST(in[k] + stbi__paeth(cur[k-img_n],prior[k],prior[k-img_n])); break;
CASE(STBI__F_avg_first) cur[k] = STBI__BYTECAST(in[k] + (cur[k-img_n] >> 1)); break;
CASE(STBI__F_paeth_first) cur[k] = STBI__BYTECAST(in[k] + stbi__paeth(cur[k-img_n],0,0)); break;
}
#undef CASE
} else {
STBI_ASSERT(img_n+1 == out_n);
#define CASE(f) \
case f: \
for (i=x-1; i >= 1; --i, cur[img_n]=255,cur+=out_n,prior+=out_n) \
for (k=0; k < img_n; ++k, ++rawk)
for (i=x-1; i >= 1; --i, cur[img_n]=255,in+=img_n,cur+=out_n,prior+=out_n) \
for (k=0; k < img_n; ++k)
switch (filter) {
CASE(STBI__F_none) cur[k] = PIXEL(raw,k); break;
CASE(STBI__F_sub) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + cur[k-out_n]); break;
CASE(STBI__F_up) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + prior[k]); break;
CASE(STBI__F_avg) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + ((prior[k] + cur[k-out_n])>>1)); break;
CASE(STBI__F_paeth) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + stbi__paeth(cur[k-out_n],prior[k],prior[k-out_n])); break;
CASE(STBI__F_avg_first) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + (cur[k-out_n] >> 1)); break;
CASE(STBI__F_paeth_first) cur[k] = STBI__BYTECAST(PIXEL(raw,rawk) + stbi__paeth(cur[k-out_n],0,0)); break;
CASE(STBI__F_none) cur[k] = in[k]; break;
CASE(STBI__F_sub) cur[k] = STBI__BYTECAST(in[k] + cur[k-out_n]); break;
CASE(STBI__F_up) cur[k] = STBI__BYTECAST(in[k] + prior[k]); break;
CASE(STBI__F_avg) cur[k] = STBI__BYTECAST(in[k] + ((prior[k] + cur[k-out_n])>>1)); break;
CASE(STBI__F_paeth) cur[k] = STBI__BYTECAST(in[k] + stbi__paeth(cur[k-out_n],prior[k],prior[k-out_n])); break;
CASE(STBI__F_avg_first) cur[k] = STBI__BYTECAST(in[k] + (cur[k-out_n] >> 1)); break;
CASE(STBI__F_paeth_first) cur[k] = STBI__BYTECAST(in[k] + stbi__paeth(cur[k-out_n],0,0)); break;
}
#undef CASE
}
raw+=(rawk+pixel_data_shift_addr_mask)>>addr_shift; // scanlines are aligned on byte boundaries
}
if (depth != 8) free(line8);
return 1;
}
static int stbi__create_png_image(stbi__png *a, stbi_uc *raw, stbi__uint32 raw_len, int out_n, int depth, int interlaced)
static int stbi__create_png_image(stbi__png *a, stbi_uc *raw, stbi__uint32 raw_len, int out_n, int depth, int color, int interlaced)
{
stbi_uc *final;
int p;
if (!interlaced)
return stbi__create_png_image_raw(a, raw, raw_len, out_n, a->s->img_x, a->s->img_y, depth);
return stbi__create_png_image_raw(a, raw, raw_len, out_n, a->s->img_x, a->s->img_y, depth, color);
// de-interlacing
final = (stbi_uc *) stbi__malloc(a->s->img_x * a->s->img_y * out_n);
@ -2609,7 +2642,7 @@ static int stbi__create_png_image(stbi__png *a, stbi_uc *raw, stbi__uint32 raw_l
x = (a->s->img_x - xorig[p] + xspc[p]-1) / xspc[p];
y = (a->s->img_y - yorig[p] + yspc[p]-1) / yspc[p];
if (x && y) {
if (!stbi__create_png_image_raw(a, raw, raw_len, out_n, x, y, depth)) {
if (!stbi__create_png_image_raw(a, raw, raw_len, out_n, x, y, depth, color)) {
free(final);
return 0;
}
@ -2749,7 +2782,7 @@ static int stbi__parse_png_file(stbi__png *z, int scan, int req_comp)
stbi_uc palette[1024], pal_img_n=0;
stbi_uc has_trans=0, tc[3];
stbi__uint32 ioff=0, idata_limit=0, i, pal_len=0;
int first=1,k,interlace=0, depth=0, is_iphone=0;
int first=1,k,interlace=0, color=0, depth=0, is_iphone=0;
stbi__context *s = z->s;
z->expanded = NULL;
@ -2768,19 +2801,14 @@ static int stbi__parse_png_file(stbi__png *z, int scan, int req_comp)
stbi__skip(s, c.length);
break;
case PNG_TYPE('I','H','D','R'): {
int color,comp,filter;
int comp,filter;
if (!first) return stbi__err("multiple IHDR","Corrupt PNG");
first = 0;
if (c.length != 13) return stbi__err("bad IHDR len","Corrupt PNG");
s->img_x = stbi__get32be(s); if (s->img_x > (1 << 24)) return stbi__err("too large","Very large image (corrupt?)");
s->img_y = stbi__get32be(s); if (s->img_y > (1 << 24)) return stbi__err("too large","Very large image (corrupt?)");
depth = stbi__get8(s);
depth = stbi__get8(s); if (depth != 1 && depth != 2 && depth != 4 && depth != 8) return stbi__err("1/2/4/8-bit only","PNG not supported: 1/2/4/8-bit only");
color = stbi__get8(s); if (color > 6) return stbi__err("bad ctype","Corrupt PNG");
if (color == 3) {
if (depth != 1 && depth != 2 && depth != 4 && depth != 8) return stbi__err("1/2/4/8-bit only","PNG not supported: 1/2/4/8-bit only for palettized images"); // support 1/2/4 bpp for palettized.
} else {
if (depth != 8) return stbi__err("8-bit only","PNG not supported: 8-bit only"); // greyscale images (color==0) would need the pixel data to be scaled (see PIXEL macro)
}
if (color == 3) pal_img_n = 3; else if (color & 1) return stbi__err("bad ctype","Corrupt PNG");
comp = stbi__get8(s); if (comp) return stbi__err("bad comp method","Corrupt PNG");
filter= stbi__get8(s); if (filter) return stbi__err("bad filter method","Corrupt PNG");
@ -2863,7 +2891,7 @@ static int stbi__parse_png_file(stbi__png *z, int scan, int req_comp)
s->img_out_n = s->img_n+1;
else
s->img_out_n = s->img_n;
if (!stbi__create_png_image(z, z->expanded, raw_len, s->img_out_n, depth, interlace)) return 0;
if (!stbi__create_png_image(z, z->expanded, raw_len, s->img_out_n, depth, color, interlace)) return 0;
if (has_trans)
if (!stbi__compute_transparency(z, tc, s->img_out_n)) return 0;
if (is_iphone && stbi__de_iphone_flag && s->img_out_n > 2)

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