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[devel] Fixes to rgb_to_gray and cHRM XYZ APIs

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This commit is contained in:
John Bowler
2011-08-25 16:19:44 -05:00
committed by Glenn Randers-Pehrson
parent 0c03fc6f75
commit 736f40f459
13 changed files with 2055 additions and 514 deletions
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388
pngrtran.c
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@@ -968,13 +968,17 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
{
png_uint_16 red_int, green_int;
/* NOTE: this calculation does not round, but this behavior is retained
* for consistency, the inaccuracy is very small. The code here always
* overwrites the coefficients, regardless of whether they have been
* defaulted or set already.
*/
red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L);
green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L);
png_ptr->rgb_to_gray_red_coeff = red_int;
png_ptr->rgb_to_gray_green_coeff = green_int;
png_ptr->rgb_to_gray_blue_coeff =
(png_uint_16)(32768 - red_int - green_int);
png_ptr->rgb_to_gray_coefficients_set = 1;
}
else
@@ -983,17 +987,18 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
png_warning(png_ptr,
"ignoring out of range rgb_to_gray coefficients");
/* Use the defaults, from the cHRM chunk if set, else the built in Rec
* 709 values (which correspond to sRGB, so we don't have to worry
* about the sRGB chunk!)
/* Use the defaults, from the cHRM chunk if set, else the historical
* values which are close to the sRGB/HDTV/ITU-Rec 709 values. See
* png_do_rgb_to_gray for more discussion of the values. In this case
* the coefficients are not marked as 'set' and are not overwritten if
* something has already provided a default.
*/
if (png_ptr->rgb_to_gray_red_coeff == 0 &&
png_ptr->rgb_to_gray_green_coeff == 0 &&
png_ptr->rgb_to_gray_blue_coeff == 0)
png_ptr->rgb_to_gray_green_coeff == 0)
{
png_ptr->rgb_to_gray_red_coeff = 6968; /* .212671 * 32768 + .5 */
png_ptr->rgb_to_gray_green_coeff = 23434; /* .715160 * 32768 + .5 */
png_ptr->rgb_to_gray_blue_coeff = 2366;
png_ptr->rgb_to_gray_red_coeff = 6968;
png_ptr->rgb_to_gray_green_coeff = 23434;
/* png_ptr->rgb_to_gray_blue_coeff = 2366; */
}
}
}
@@ -1401,7 +1406,7 @@ png_init_read_transformations(png_structp png_ptr)
if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
{
/* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
* the file was greyscale the background value is gray.
* the file was grayscale the background value is gray.
*/
if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
@@ -3089,26 +3094,38 @@ png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
*
* Y = (6966 * R + 23436 * G + 2366 * B)/32768
*
* We use the approximation
* Historically, however, libpng uses numbers derived from the ITU-R Rec 709
* end point chromaticities and the D65 white point. Depending on the
* precision used for the D65 white point this produces a variety of different
* numbers, however if the four decimal place value used in ITU-R Rec 709 is
* used (0.3127,0.3290) the Y calculation would be:
*
* Y = (6968 * R + 23435 * G + 2366 * B)/32768
*
* While this is correct the rounding results in an overflow for white, because
* the sum of the rounded coefficients is 32769, not 32768. Consequently
* libpng uses, instead, the closest non-overflowing approximation:
*
* Y = (6968 * R + 23434 * G + 2366 * B)/32768
*
* Starting with libpng-1.5.4, if the image being converted has the
* sRGB chunk, then the sRGB numbers are used by default:
* Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
* (including an sRGB chunk) then the chromaticities are used to calculate the
* coefficients. See the chunk handling in pngrutil.c for more information.
*
* Y = 0.33000*R + 0.60000*G + 0.06000*B
* In all cases the calculation is to be done in a linear colorspace. If no
* gamma information is available to correct the encoding of the original RGB
* values this results in an implicit assumption that the original PNG RGB
* values were linear.
*
* The calculation is to be done in a linear colorspace.
*
* Other integer coefficents can be used via png_set_rgb_to_gray().
* Other integer coefficents can be used via png_set_rgb_to_gray(). Because
* the API takes just red and green coefficients the blue coefficient is
* calculated to make the sum 32768. This will result in different rounding
* to that used above.
*/
int /* PRIVATE */
png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
{
png_uint_32 i;
png_uint_32 row_width = row_info->width;
int rgb_error = 0;
png_debug(1, "in png_do_rgb_to_gray");
@@ -3116,234 +3133,179 @@ png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
(row_info->color_type & PNG_COLOR_MASK_COLOR))
{
png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
png_uint_32 bc = png_ptr->rgb_to_gray_blue_coeff;
PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
PNG_CONST png_uint_32 bc = 32768 - rc - gc;
PNG_CONST png_uint_32 row_width = row_info->width;
PNG_CONST int have_alpha =
(row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
if (row_info->color_type == PNG_COLOR_TYPE_RGB)
if (row_info->bit_depth == 8)
{
if (row_info->bit_depth == 8)
{
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
/* Notice that gamma to/from 1 are not necessarily inverses (if
* there is an overall gamma correction). Prior to 1.5.5 this code
* checked the linearized values for equality; this doesn't match
* the documentation, the original values must be checked.
*/
if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
{
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_bytep sp = row;
png_bytep dp = row;
png_byte red = *(sp++);
png_byte green = *(sp++);
png_byte blue = *(sp++);
for (i = 0; i < row_width; i++)
if (red != green || red != blue)
{
png_byte red = png_ptr->gamma_to_1[*(sp++)];
png_byte green = png_ptr->gamma_to_1[*(sp++)];
png_byte blue = png_ptr->gamma_to_1[*(sp++)];
red = png_ptr->gamma_to_1[red];
green = png_ptr->gamma_to_1[green];
blue = png_ptr->gamma_to_1[blue];
if (red != green || red != blue)
{
rgb_error |= 1;
*(dp++) = png_ptr->gamma_from_1[
(rc*red + gc*green + bc*blue)>>15];
}
else
*(dp++) = *(sp - 1);
rgb_error |= 1;
*(dp++) = png_ptr->gamma_from_1[
(rc*red + gc*green + bc*blue + 16384)>>15];
}
}
else
#endif
{
png_bytep sp = row;
png_bytep dp = row;
for (i = 0; i < row_width; i++)
else
{
png_byte red = *(sp++);
png_byte green = *(sp++);
png_byte blue = *(sp++);
/* If there is no overall correction the table will not be
* set.
*/
if (png_ptr->gamma_table != NULL)
red = png_ptr->gamma_table[red];
if (red != green || red != blue)
{
rgb_error |= 1;
*(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
}
else
*(dp++) = *(sp - 1);
*(dp++) = red;
}
if (have_alpha)
*(dp++) = *(sp++);
}
}
else /* RGB bit_depth == 16 */
else
#endif
{
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
if (png_ptr->gamma_16_to_1 != NULL &&
png_ptr->gamma_16_from_1 != NULL)
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_bytep sp = row;
png_bytep dp = row;
for (i = 0; i < row_width; i++)
png_byte red = *(sp++);
png_byte green = *(sp++);
png_byte blue = *(sp++);
if (red != green || red != blue)
{
png_uint_16 red, green, blue, w;
rgb_error |= 1;
/*NOTE: this is the historical approach which simply
* truncates the results.
*/
*(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
}
red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
else
*(dp++) = red;
if (red == green && red == blue)
w = red;
if (have_alpha)
*(dp++) = *(sp++);
}
}
}
else
{
png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red&0xff)
else /* RGB bit_depth == 16 */
{
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
{
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_uint_16 red, green, blue, w;
red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
if (red == green && red == blue)
{
if (png_ptr->gamma_16_table != NULL)
w = png_ptr->gamma_16_table[(red&0xff)
>> png_ptr->gamma_shift][red>>8];
png_uint_16 green_1 =
png_ptr->gamma_16_to_1[(green&0xff) >>
png_ptr->gamma_shift][green>>8];
png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue&0xff)
>> png_ptr->gamma_shift][blue>>8];
png_uint_16 gray16 = (png_uint_16)((rc*red_1 + gc*green_1
+ bc*blue_1)>>15);
w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
png_ptr->gamma_shift][gray16 >> 8];
rgb_error |= 1;
}
*(dp++) = (png_byte)((w>>8) & 0xff);
*(dp++) = (png_byte)(w & 0xff);
}
}
else
#endif
{
png_bytep sp = row;
png_bytep dp = row;
for (i = 0; i < row_width; i++)
{
png_uint_16 red, green, blue, gray16;
red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
if (red != green || red != blue)
rgb_error |= 1;
gray16 = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
*(dp++) = (png_byte)((gray16>>8) & 0xff);
*(dp++) = (png_byte)(gray16 & 0xff);
}
}
}
}
if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
{
if (row_info->bit_depth == 8)
{
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
{
png_bytep sp = row;
png_bytep dp = row;
for (i = 0; i < row_width; i++)
{
png_byte red = png_ptr->gamma_to_1[*(sp++)];
png_byte green = png_ptr->gamma_to_1[*(sp++)];
png_byte blue = png_ptr->gamma_to_1[*(sp++)];
if (red != green || red != blue)
rgb_error |= 1;
*(dp++) = png_ptr->gamma_from_1
[(rc*red + gc*green + bc*blue)>>15];
*(dp++) = *(sp++); /* alpha */
}
}
else
#endif
{
png_bytep sp = row;
png_bytep dp = row;
for (i = 0; i < row_width; i++)
{
png_byte red = *(sp++);
png_byte green = *(sp++);
png_byte blue = *(sp++);
if (red != green || red != blue)
rgb_error |= 1;
*(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
*(dp++) = *(sp++); /* alpha */
}
}
}
else /* RGBA bit_depth == 16 */
{
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
if (png_ptr->gamma_16_to_1 != NULL &&
png_ptr->gamma_16_from_1 != NULL)
{
png_bytep sp = row;
png_bytep dp = row;
for (i = 0; i < row_width; i++)
{
png_uint_16 red, green, blue, w;
red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
if (red == green && red == blue)
w = red;
else
{
png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red&0xff) >>
png_ptr->gamma_shift][red>>8];
w = red;
}
png_uint_16 green_1 =
png_ptr->gamma_16_to_1[(green&0xff) >>
png_ptr->gamma_shift][green>>8];
else
{
png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red&0xff)
>> png_ptr->gamma_shift][red>>8];
png_uint_16 green_1 =
png_ptr->gamma_16_to_1[(green&0xff) >>
png_ptr->gamma_shift][green>>8];
png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue&0xff)
>> png_ptr->gamma_shift][blue>>8];
png_uint_16 gray16 = (png_uint_16)((rc*red_1 + gc*green_1
+ bc*blue_1 + 16384)>>15);
w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
png_ptr->gamma_shift][gray16 >> 8];
rgb_error |= 1;
}
png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue&0xff) >>
png_ptr->gamma_shift][blue>>8];
*(dp++) = (png_byte)((w>>8) & 0xff);
*(dp++) = (png_byte)(w & 0xff);
png_uint_16 gray16 = (png_uint_16)((rc * red_1
+ gc * green_1 + bc * blue_1)>>15);
w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
png_ptr->gamma_shift][gray16 >> 8];
rgb_error |= 1;
}
*(dp++) = (png_byte)((w>>8) & 0xff);
*(dp++) = (png_byte)(w & 0xff);
*(dp++) = *(sp++); /* alpha */
if (have_alpha)
{
*(dp++) = *(sp++);
*(dp++) = *(sp++);
}
}
else
}
else
#endif
{
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_bytep sp = row;
png_bytep dp = row;
for (i = 0; i < row_width; i++)
png_uint_16 red, green, blue, gray16;
red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
if (red != green || red != blue)
rgb_error |= 1;
/* From 1.5.5 in the 16 bit case do the accurate convertion even
* in the 'fast' case - this is because this is where the code
* ends up when handling linear 16 bit data.
*/
gray16 = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
15);
*(dp++) = (png_byte)((gray16>>8) & 0xff);
*(dp++) = (png_byte)(gray16 & 0xff);
if (have_alpha)
{
png_uint_16 red, green, blue, gray16;
red = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
if (red != green || red != blue)
rgb_error |= 1;
gray16 = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
*(dp++) = (png_byte)((gray16>>8) & 0xff);
*(dp++) = (png_byte)(gray16 & 0xff);
*(dp++) = *(sp++); /* alpha */
*(dp++) = *(sp++);
*(dp++) = *(sp++);
}
}
}
}
row_info->channels -= 2;
row_info->color_type = (png_byte)(row_info->color_type &
~PNG_COLOR_MASK_COLOR);