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stb_image.h: Fix TGA colormap support

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* Calculate correct stb format (incl. proper 16bit support) also when
  using a colormap (palette)
* Create colormap with tga_comp, to correctly support 16bit RGB
  (instead of using tga_palette_bits/8 and just copying the data)
* For TGAs with colormap, the TGA bits per pixel field specifies the
  size of an index to the colormap - the "real" color depth
  of the image is saved in the color map specification's bits per pixel
  field. I think only 8 and 16bit indices make sense (16 should be
  supported, otherwise the colormap length could be u8 instead of u16),
  so I added support for both.
* Helper functions stbi__tga_get_comp() to calculate stb pixelformat and
  stbi__tga_read_rgb16() to read one 16bit pixel and convert it to
  24/32bit RGB(A) - for less duplicate code
master
Daniel Gibson ago%!(EXTRA string=10 years)
parent 57409c3d15
commit d235049322
1 changed files with 74 additions and 60 deletions
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  1. 134
      stb_image.h

134
stb_image.h
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@ -4811,6 +4811,26 @@ static stbi_uc *stbi__bmp_load(stbi__context *s, int *x, int *y, int *comp, int
// Targa Truevision - TGA
// by Jonathan Dummer
#ifndef STBI_NO_TGA
// returns STBI_rgb or whatever, 0 on error
static int stbi__tga_get_comp(int bits_per_pixel, int alpha_bits, int is_grey, int* is_rgb16)
{
// only RGB or RGBA (incl. 16bit) or grey allowed
if(is_rgb16) *is_rgb16 = 0;
switch(bits_per_pixel) {
case 8: return STBI_grey;
case 15: if(is_rgb16) *is_rgb16 = 1; return STBI_rgb;
case 16:
if(is_grey) return STBI_grey_alpha;
else {
if(is_rgb16) *is_rgb16 = 1;
return alpha_bits ? STBI_rgb_alpha : STBI_rgb; // most signif. bit might be for alpha
}
case 24: // fall-through
case 32: return bits_per_pixel/8;
default: return 0;
}
}
static int stbi__tga_info(stbi__context *s, int *x, int *y, int *comp)
{
int tga_w, tga_h, tga_comp, tga_image_type, tga_bits_per_pixel, tga_colormap_bpp;
@ -4854,6 +4874,7 @@ static int stbi__tga_info(stbi__context *s, int *x, int *y, int *comp)
return 0; // test height
}
tga_bits_per_pixel = stbi__get8(s); // bits per pixel
sz = stbi__get8(s) & 15; // alpha bits
if (tga_colormap_bpp != 0) {
if((tga_bits_per_pixel != 8) && (tga_bits_per_pixel != 16)) {
// when using a colormap, tga_bits_per_pixel is the size of the indexes
@ -4861,20 +4882,13 @@ static int stbi__tga_info(stbi__context *s, int *x, int *y, int *comp)
stbi__rewind(s);
return 0;
}
tga_bits_per_pixel = tga_colormap_bpp; // make sure colormap's bpp are tested for tga_comp
tga_comp = stbi__tga_get_comp(tga_colormap_bpp, sz, 0, NULL);
} else {
tga_comp = stbi__tga_get_comp(tga_bits_per_pixel, sz, (tga_image_type == 3) || (tga_image_type == 11), NULL);
}
sz = stbi__get8(s) & 15; // alpha bits
// only RGB or RGBA (incl. 16bit) or grey allowed
switch(tga_bits_per_pixel) {
case 8: tga_comp = STBI_grey; break;
case 15: tga_comp = STBI_rgb; break;
case 16:
if((tga_image_type == 3) || (tga_image_type == 11)) tga_comp = STBI_grey_alpha;
else tga_comp = sz ? STBI_rgb_alpha : STBI_rgb; // most signif. bit might be for alpha
break;
case 24: // fall-through
case 32: tga_comp = tga_bits_per_pixel/8; break;
default: stbi__rewind(s); return 0;
if(!tga_comp) {
stbi__rewind(s);
return 0;
}
if (x) *x = tga_w;
if (y) *y = tga_h;
@ -4913,6 +4927,27 @@ errorEnd:
return res;
}
// read 16bit value and convert to 24/32bit RGB(A)
void stbi__tga_read_rgb16(stbi__context *s, int has_alpha, stbi_uc* out)
{
stbi__uint16 px = stbi__get16le(s);
stbi__uint16 fiveBitMask = 31;
// we have 3 channels with 5bits each
int r = (px >> 10) & fiveBitMask;
int g = (px >> 5) & fiveBitMask;
int b = px & fiveBitMask;
// Note that this saves the data in RGB(A) order, so it doesn't need to be swapped later
out[0] = (r * 255)/31;
out[1] = (g * 255)/31;
out[2] = (b * 255)/31;
if(has_alpha) {
// most significant bit set to 1 for opaque, 0 for trans., according to
// http://www.imagemagick.org/discourse-server/viewtopic.php?t=27469
out[3] = !(px & 0x8000) * 255;
}
}
static stbi_uc *stbi__tga_load(stbi__context *s, int *x, int *y, int *comp, int req_comp)
{
// read in the TGA header stuff
@ -4949,21 +4984,11 @@ static stbi_uc *stbi__tga_load(stbi__context *s, int *x, int *y, int *comp, int
tga_inverted = 1 - ((tga_inverted >> 5) & 1);
// If I'm paletted, then I'll use the number of bits from the palette
if ( tga_indexed )
{
tga_comp = tga_palette_bits / 8;
}
else {
switch(tga_bits_per_pixel) {
case 8: tga_comp = STBI_grey; break;
case 15: tga_comp = STBI_rgb; tga_rgb16=1; break;
case 16:
if (tga_image_type == 3) tga_comp = STBI_grey_alpha;
else { tga_comp = tga_alpha_bits ? STBI_rgb_alpha : STBI_rgb; tga_rgb16=1; }
break;
default: tga_comp = tga_bits_per_pixel / 8; // incl. 24 and 32
}
}
if ( tga_indexed ) tga_comp = stbi__tga_get_comp(tga_palette_bits, tga_alpha_bits, 0, &tga_rgb16);
else tga_comp = stbi__tga_get_comp(tga_bits_per_pixel, tga_alpha_bits, (tga_image_type == 3), &tga_rgb16);
if(!tga_comp) // shouldn't really happen, stbi__tga_test() should have ensured basic consistency
return stbi__errpuc("bad format", "Can't find out TGA pixelformat");
// tga info
*x = tga_width;
@ -4989,15 +5014,22 @@ static stbi_uc *stbi__tga_load(stbi__context *s, int *x, int *y, int *comp, int
// any data to skip? (offset usually = 0)
stbi__skip(s, tga_palette_start );
// load the palette
tga_palette = (unsigned char*)stbi__malloc( tga_palette_len * tga_palette_bits / 8 );
tga_palette = (unsigned char*)stbi__malloc( tga_palette_len * tga_comp );
if (!tga_palette) {
STBI_FREE(tga_data);
return stbi__errpuc("outofmem", "Out of memory");
}
if (!stbi__getn(s, tga_palette, tga_palette_len * tga_palette_bits / 8 )) {
STBI_FREE(tga_data);
STBI_FREE(tga_palette);
return stbi__errpuc("bad palette", "Corrupt TGA");
if (tga_rgb16) {
stbi_uc *pal_entry = tga_palette;
STBI_ASSERT(tga_comp == STBI_rgb || tga_comp == STBI_rgb_alpha);
for (i=0; i < tga_palette_len; ++i) {
stbi__tga_read_rgb16(s, tga_comp == STBI_rgb_alpha, pal_entry);
pal_entry += tga_comp;
}
} else if (!stbi__getn(s, tga_palette, tga_palette_len * tga_comp)) {
STBI_FREE(tga_data);
STBI_FREE(tga_palette);
return stbi__errpuc("bad palette", "Corrupt TGA");
}
}
// load the data
@ -5027,39 +5059,21 @@ static stbi_uc *stbi__tga_load(stbi__context *s, int *x, int *y, int *comp, int
// load however much data we did have
if ( tga_indexed )
{
// read in 1 byte, then perform the lookup
int pal_idx = stbi__get8(s);
if ( pal_idx >= tga_palette_len )
{
// invalid index
// read in index, then perform the lookup
int pal_idx = (tga_bits_per_pixel == 8) ? stbi__get8(s) : stbi__get16le(s);
if ( pal_idx >= tga_palette_len ) {
// invalid index
pal_idx = 0;
}
pal_idx *= tga_bits_per_pixel / 8;
for (j = 0; j*8 < tga_bits_per_pixel; ++j)
{
pal_idx *= tga_comp;
for (j = 0; j < tga_comp; ++j) {
raw_data[j] = tga_palette[pal_idx+j];
}
} else if(tga_rgb16) {
// convert from 16bit RGB(A) to 24/32bit RGB(A)
stbi__uint16 px = stbi__get16le(s);
stbi__uint16 fiveBitMask = 31;
// we have 3 channels with 5bits each
int r = (px >> 10) & fiveBitMask;
int g = (px >> 5) & fiveBitMask;
int b = px & fiveBitMask;
raw_data[0] = (r * 255)/31;
raw_data[1] = (g * 255)/31;
raw_data[2] = (b * 255)/31;
if(tga_comp == STBI_rgb_alpha) {
// most significant bit set to 1 for opaque, 0 for trans., according to
// http://www.imagemagick.org/discourse-server/viewtopic.php?t=27469
raw_data[3] = !(px & 0x8000) * 255;
}
stbi__tga_read_rgb16(s, tga_comp == STBI_rgb_alpha, raw_data);
} else {
// read in the data raw
for (j = 0; j*8 < tga_bits_per_pixel; ++j)
{
for (j = 0; j < tga_comp; ++j) {
raw_data[j] = stbi__get8(s);
}
}
@ -5098,7 +5112,7 @@ static stbi_uc *stbi__tga_load(stbi__context *s, int *x, int *y, int *comp, int
}
}
// swap RGB
// swap RGB - if the source data was RGB16, it already is in the right order
if (tga_comp >= 3 && !tga_rgb16)
{
unsigned char* tga_pixel = tga_data;

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