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get/set resolution in png files

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This commit is contained in:
John Cupitt 2011-01-06 12:18:40 +00:00
parent 6425cd2660
commit ea99beb727
3 changed files with 34 additions and 1 deletions
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1
ChangeLog
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@ -3,6 +3,7 @@
- faster tiff read for some common cases
- faster im_tile_cache()
- add -lstdc++ to vips-7.xx.pc, if we used it
- im_vips2png() / im_png2vips() set / get png resolution (thanks Zhiyu Wu)
30/11/10 started 7.24.0
- bump for new stable

26
libvips/format/im_png2vips.c
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@ -16,6 +16,8 @@
* - small cleanups
* 4/2/10
* - gtkdoc
* 8/1/11
* - get png resolution (thanks Zhiyu Wu)
*/
/*
@ -229,6 +231,9 @@ static int
png2vips( Read *read, int header_only )
{
int bands, bpp, type;
png_uint_32 res_x, res_y;
int unit_type;
double Xres, Yres;
if( setjmp( read->pPng->jmpbuf ) )
return( -1 );
@ -296,13 +301,32 @@ png2vips( Read *read, int header_only )
if( read->pInfo->bit_depth > 8 && !im_amiMSBfirst() )
png_set_swap( read->pPng );
/* Get resolution. I'm not sure what we should do for UNKNOWN, since
* vips is always pixels/mm.
*/
png_get_pHYs( read->pPng, read->pInfo,
&res_x, &res_y, &unit_type );
switch( unit_type ) {
case PNG_RESOLUTION_METER:
Xres = res_x / 1000.0;
Yres = res_y / 1000.0;
break;
default:
Xres = res_x;
Yres = res_y;
break;
}
/* Set VIPS header.
*/
im_initdesc( read->out,
read->pInfo->width, read->pInfo->height, bands,
bpp == 1 ? IM_BBITS_BYTE : IM_BBITS_SHORT,
bpp == 1 ? IM_BANDFMT_UCHAR : IM_BANDFMT_USHORT,
IM_CODING_NONE, type, 1.0, 1.0, 0, 0 );
IM_CODING_NONE, type,
Xres, Yres,
0, 0 );
if( !header_only ) {
if( png_set_interlace_handling( read->pPng ) > 1 ) {

8
libvips/format/im_vips2png.c
View File

@ -19,6 +19,8 @@
* - lololo but broke 8-bit save, fixed again
* 20/7/10 Tim Elliott
* - added im_vips2bufpng()
* 8/1/11
* - set png resolution (thanks Zhiyu Wu)
*/
/*
@ -255,6 +257,12 @@ write_vips( Write *write, int compress, int interlace )
g_assert( 0 );
}
/* Set resolution. libpnbg uses pixels per meter.
*/
png_set_pHYs( write->pPng, write->pInfo,
IM_RINT( in->Xres * 1000 ), IM_RINT( in->Yres * 1000 ),
PNG_RESOLUTION_METER );
png_write_info( write->pPng, write->pInfo );
/* If we're an intel byte order CPU and this is a 16bit image, we need