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better handling of JFIF res unit 0 

res unit 0 sets the aspect ratio, rather than being unitless

thanks angelmixu

see https://github.com/libvips/libvips/issues/1641
This commit is contained in:
John Cupitt 2020-05-05 11:47:31 +01:00
parent 8281416ca4
commit 77365a8a6f
1 changed files with 8 additions and 5 deletions
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13
libvips/foreign/jpeg2vips.c
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@ -106,6 +106,8 @@
* - restart after minimise
* 14/10/19
* - revise for source IO
* 5/5/20 angelmixu
* - better handling of JFIF res unit 0
*/
/*
@ -512,16 +514,17 @@ read_jpeg_header( ReadJpeg *jpeg, VipsImage *out )
cinfo->X_density != 1U &&
cinfo->Y_density != 1U ) {
#ifdef DEBUG
printf( "read_jpeg_header: seen jfif _density %d, %d\n",
cinfo->X_density, cinfo->Y_density );
printf( "read_jpeg_header: jfif _density %d, %d, unit %d\n",
cinfo->X_density, cinfo->Y_density,
cinfo->density_unit );
#endif /*DEBUG*/
switch( cinfo->density_unit ) {
case 0:
/* None. Just set.
/* X_density / Y_density gives the pixel aspect ratio.
* Leave xres, but adjust yres.
*/
xres = cinfo->X_density;
yres = cinfo->Y_density;
yres = xres * cinfo->X_density / cinfo->Y_density;
break;
case 1: