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png: Add support for 16 bpc png reading as floating point format

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Similar to writing png, don't squash 16 bpc to 8 bpc and create
a float surface to contain the image.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Bryce Harrington <bryce@bryceharrington.org>
This commit is contained in:
Maarten Lankhorst 2018-12-03 15:13:42 +01:00 • committed by Bryce Harrington
parent 1df0a68460
commit d061570a70
1 changed files with 60 additions and 8 deletions
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68
src/cairo-png.c
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@ -142,6 +142,33 @@ unpremultiply_float (float *f, uint16_t *d16, unsigned width)
}
}
static void
premultiply_float (float *f, const uint16_t *d16, unsigned int width)
{
unsigned int i = width;
/* Convert d16 in place back to float */
while (i--) {
float a = d16[i * 4 + 3] / 65535.f;
f[i * 4 + 3] = a;
f[i * 4 + 2] = (float)d16[i * 4 + 2] / 65535.f * a;
f[i * 4 + 1] = (float)d16[i * 4 + 1] / 65535.f * a;
f[i * 4] = (float)d16[i * 4] / 65535.f * a;
}
}
static void convert_u16_to_float (float *f, const uint16_t *d16, unsigned int width)
{
/* Convert d16 in place back to float */
unsigned int i = width;
while (i--) {
f[i * 3 + 2] = (float)d16[i * 4 + 2] / 65535.f;
f[i * 3 + 1] = (float)d16[i * 4 + 1] / 65535.f;
f[i * 3] = (float)d16[i * 4] / 65535.f;
}
}
static void
convert_float_to_u16 (float *f, uint16_t *d16, unsigned int width)
@ -700,9 +727,6 @@ read_png (struct png_read_closure_t *png_closure)
if (png_get_valid (png, info, PNG_INFO_tRNS))
png_set_tRNS_to_alpha (png);
if (depth == 16)
png_set_strip_16 (png);
if (depth < 8)
png_set_packing (png);
@ -723,7 +747,7 @@ read_png (struct png_read_closure_t *png_closure)
png_get_IHDR (png, info,
&png_width, &png_height, &depth,
&color_type, &interlace, NULL, NULL);
if (depth != 8 ||
if ((depth != 8 && depth != 16) ||
! (color_type == PNG_COLOR_TYPE_RGB ||
color_type == PNG_COLOR_TYPE_RGB_ALPHA))
{
@ -737,13 +761,21 @@ read_png (struct png_read_closure_t *png_closure)
/* fall-through just in case ;-) */
case PNG_COLOR_TYPE_RGB_ALPHA:
format = CAIRO_FORMAT_ARGB32;
png_set_read_user_transform_fn (png, premultiply_data);
if (depth == 8) {
format = CAIRO_FORMAT_ARGB32;
png_set_read_user_transform_fn (png, premultiply_data);
} else {
format = CAIRO_FORMAT_RGBA128F;
}
break;
case PNG_COLOR_TYPE_RGB:
format = CAIRO_FORMAT_RGB24;
png_set_read_user_transform_fn (png, convert_bytes_to_data);
if (depth == 8) {
format = CAIRO_FORMAT_RGB24;
png_set_read_user_transform_fn (png, convert_bytes_to_data);
} else {
format = CAIRO_FORMAT_RGB96F;
}
break;
}
@ -776,6 +808,26 @@ read_png (struct png_read_closure_t *png_closure)
goto BAIL;
}
if (format == CAIRO_FORMAT_RGBA128F) {
i = png_height;
while (i--) {
float *float_line = (float *)row_pointers[i];
uint16_t *u16_line = (uint16_t *)row_pointers[i];
premultiply_float (float_line, u16_line, png_width);
}
} else if (format == CAIRO_FORMAT_RGB96F) {
i = png_height;
while (i--) {
float *float_line = (float *)row_pointers[i];
uint16_t *u16_line = (uint16_t *)row_pointers[i];
convert_u16_to_float (float_line, u16_line, png_width);
}
}
surface = cairo_image_surface_create_for_data (data, format,
png_width, png_height,
stride);