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better png import

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better handling of 1-bit and palette png images, though png 1.2.9 and
later only now argh
This commit is contained in:
John Cupitt 2011-03-20 11:28:17 +00:00
parent 3ae641b320
commit 0dfd37b036
3 changed files with 20 additions and 16 deletions
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6
TODO
View File

@ -5,6 +5,12 @@
a 1-bit PNG image ... we get 0/1 in the vips file, argh, not 0/255
- try:
http://upload.wikimedia.org/wikipedia/commons/3/31/A_large_blank_world_map_with_oceans_marked_in_blue-edited.png
pallette png, we just get RGBA all zero atm
- vips_attach_save() in image.c has problems if save fails ... there's no way
for the result of the "written" callback to propogate the error

3
configure.in
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@ -495,7 +495,7 @@ AC_ARG_WITH([png],
AS_HELP_STRING([--without-png], [build without libpng (default: test)]))
if test x"$with_png" != "xno"; then
PKG_CHECK_MODULES(PNG, libpng,
PKG_CHECK_MODULES(PNG, libpng >= 1.2.9,
[AC_DEFINE(HAVE_PNG,1,[define if you have libpng installed.])
with_png=yes
PACKAGES_USED="$PACKAGES_USED libpng"],
@ -683,6 +683,7 @@ file import with matio: $with_matio
file import with cfitsio: $with_cfitsio
text rendering with pangoft2: $with_pangoft2
file import/export with libpng: $with_png
(requires libpng-1.2.9 or later)
file import/export with libtiff: $with_tiff
file import/export with libjpeg: $with_jpeg
use libexif to load/save JPEG metadata: $with_libexif

27
libvips/format/im_png2vips.c
View File

@ -20,6 +20,8 @@
* - get png resolution (thanks Zhiyu Wu)
* 17/3/11
* - update for libpng-1.5 API changes
* - better handling of palette and 1-bit images
* - ... but we are now png 1.2.9 and later only :-( argh
*/
/*
@ -64,8 +66,7 @@
int
im_png2vips( const char *name, IMAGE *out )
{
im_error( "im_png2vips", "%s",
_( "PNG support disabled" ) );
im_error( "im_png2vips", "%s", _( "PNG support disabled" ) );
return( -1 );
}
@ -236,8 +237,6 @@ png2vips( Read *read, int header_only )
{
png_uint_32 width, height;
int bit_depth, color_type, interlace_type;
int num_trans;
png_color_8p sig_bit;
png_uint_32 res_x, res_y;
int unit_type;
@ -253,8 +252,6 @@ png2vips( Read *read, int header_only )
png_get_IHDR( read->pPng, read->pInfo,
&width, &height, &bit_depth, &color_type,
&interlace_type, NULL, NULL );
png_get_tRNS( read->pPng, read->pInfo, NULL, &num_trans, NULL );
png_get_sBIT( read->pPng, read->pInfo, &sig_bit );
/* png_get_channels() gives us 1 band for palette images ... so look
* at colour_type for output bands.
@ -263,10 +260,9 @@ png2vips( Read *read, int header_only )
case PNG_COLOR_TYPE_PALETTE:
bands = 3;
/* Don't know if this is really correct. If there are
* transparent pixels, assume we're going to output RGBA.
/* If there's transparency in the palette, we make an alpha.
*/
if( num_trans )
if( png_get_valid( read->pPng, read->pInfo, PNG_INFO_tRNS ) )
bands = 4;
break;
@ -309,17 +305,18 @@ png2vips( Read *read, int header_only )
type = IM_TYPE_sRGB;
}
/* Expand palette images.
/* Expand palette images, expand transparency too.
*/
if( color_type == PNG_COLOR_TYPE_PALETTE )
png_set_expand( read->pPng );
png_set_palette_to_rgb( read->pPng );
if( png_get_valid( read->pPng, read->pInfo, PNG_INFO_tRNS ) )
png_set_tRNS_to_alpha( read->pPng );
/* Expand <8 bit images to full bytes.
*/
if( bit_depth < 8 ) {
png_set_packing( read->pPng );
png_set_shift( read->pPng, sig_bit );
}
if( color_type == PNG_COLOR_TYPE_GRAY &&
bit_depth < 8 )
png_set_expand_gray_1_2_4_to_8( read->pPng );
/* If we're an INTEL byte order machine and this is 16bits, we need
* to swap bytes.