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Merge pull request #2120 from libvips/revise-premultiply

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Revise premultiply
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John Cupitt 2021-03-06 10:25:20 +00:00 committed by GitHub
commit 81dffdd571
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8 changed files with 172 additions and 114 deletions
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2
ChangeLog
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@ -7,6 +7,8 @@
- fix includes of glib headers in C++ [lovell]
- fix build with more modern librsvg [lovell]
- fix a possible segv with very wide images [f1ac]
- revise premultiply, again [jjonesrs]
- revise profile handling in vipsthumbnail
- fix tiff deflate predictor setting [Adios]
18/12/20 started 8.10.5

2
libvips/conversion/flatten.c
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@ -67,7 +67,7 @@ typedef struct _VipsFlatten {
*/
VipsArrayDouble *background;
/* The [double] converted to the input image format.
/* The [double] background converted to the input image format.
*/
VipsPel *ink;

39
libvips/conversion/unpremultiply.c
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@ -7,6 +7,8 @@
* - max_alpha defaults to 65535 for RGB16/GREY16
* 24/11/17 lovell
* - match normalised alpha to output type
* 27/2/21 jjonesrs
* - revise range clipping and 1/x, again
*/
/*
@ -70,7 +72,8 @@ typedef VipsConversionClass VipsUnpremultiplyClass;
G_DEFINE_TYPE( VipsUnpremultiply, vips_unpremultiply, VIPS_TYPE_CONVERSION );
/* Unpremultiply an N-band image.
/* Unpremultiply an N-band image. Don't use clip_alpha to calculate factor: we
* want over and undershoots on alpha and RGB to cancel.
*/
#define UNPRE_MANY( IN, OUT ) { \
IN * restrict p = (IN *) in; \
@ -78,18 +81,11 @@ G_DEFINE_TYPE( VipsUnpremultiply, vips_unpremultiply, VIPS_TYPE_CONVERSION );
\
for( x = 0; x < width; x++ ) { \
IN alpha = p[alpha_band]; \
OUT factor = alpha == 0 ? 0 : max_alpha / alpha; \
\
if( alpha != 0 ) { \
OUT factor = max_alpha / alpha; \
\
for( i = 0; i < alpha_band; i++ ) \
q[i] = factor * p[i]; \
q[alpha_band] = alpha; \
} \
else \
for( i = 0; i < alpha_band + 1; i++ ) \
q[i] = 0; \
\
for( i = 0; i < alpha_band; i++ ) \
q[i] = factor * p[i]; \
q[alpha_band] = VIPS_CLIP( 0, alpha, max_alpha ); \
for( i = alpha_band + 1; i < bands; i++ ) \
q[i] = p[i]; \
\
@ -106,21 +102,12 @@ G_DEFINE_TYPE( VipsUnpremultiply, vips_unpremultiply, VIPS_TYPE_CONVERSION );
\
for( x = 0; x < width; x++ ) { \
IN alpha = p[3]; \
OUT factor = alpha == 0 ? 0 : max_alpha / alpha; \
\
if( alpha != 0 ) { \
OUT factor = max_alpha / alpha; \
\
q[0] = factor * p[0]; \
q[1] = factor * p[1]; \
q[2] = factor * p[2]; \
q[3] = alpha; \
} \
else { \
q[0] = 0; \
q[1] = 0; \
q[2] = 0; \
q[3] = 0; \
} \
q[0] = factor * p[0]; \
q[1] = factor * p[1]; \
q[2] = factor * p[2]; \
q[3] = VIPS_CLIP( 0, alpha, max_alpha ); \
\
p += 4; \
q += 4; \

228
libvips/resample/thumbnail.c
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@ -30,6 +30,9 @@
* - add thumbnail_source
* 2/6/20
* - add subifd pyr support
* 27/2/21
* - simplify rules re. processing space, colour management and linear
* mode
*/
/*
@ -626,16 +629,19 @@ vips_thumbnail_build( VipsObject *object )
int preshrunk_page_height;
double hshrink;
double vshrink;
VipsInterpretation interpretation;
/* TRUE if we've done the import of an ICC transform and still need to
* export.
*/
gboolean have_imported;
/* TRUE if we've premultiplied and need to unpremultiply.
/* If we shrink in linear space, we need to return to the input
* colourspace after the shrink.
*/
VipsInterpretation input_interpretation;
/* The format we need to revert to after unpremultiply.
*/
gboolean have_premultiplied;
VipsBandFormat unpremultiplied_format;
#ifdef DEBUG
@ -681,60 +687,78 @@ vips_thumbnail_build( VipsObject *object )
in = t[12];
}
/* In linear mode, we import right at the start.
*
* We also have to import the whole image if it's CMYK, since
* vips_colourspace() (see below) doesn't let you specify the fallback
* profile.
*
* This is only going to work for images in device space. If you have
* an image in PCS which also has an attached profile, strange things
* will happen.
/* In linear mode, we need to transform to a linear space before
* vips_resize().
*/
have_imported = FALSE;
if( thumbnail->linear &&
in->Coding == VIPS_CODING_NONE &&
(in->BandFmt == VIPS_FORMAT_UCHAR ||
in->BandFmt == VIPS_FORMAT_USHORT) &&
(vips_image_get_typeof( in, VIPS_META_ICC_NAME ) ||
thumbnail->import_profile) ) {
g_info( "importing to XYZ PCS" );
if( thumbnail->import_profile )
g_info( "fallback input profile %s",
thumbnail->import_profile );
if( thumbnail->linear ) {
/* If we are doing colour management (there's an import
* profile), then we can use XYZ PCS as the resize space.
*/
if( in->Coding == VIPS_CODING_NONE &&
(in->BandFmt == VIPS_FORMAT_UCHAR ||
in->BandFmt == VIPS_FORMAT_USHORT) &&
(vips_image_get_typeof( in, VIPS_META_ICC_NAME ) ||
thumbnail->import_profile) ) {
g_info( "importing to XYZ PCS" );
if( thumbnail->import_profile )
g_info( "fallback input profile %s",
thumbnail->import_profile );
if( vips_icc_import( in, &t[1],
"input_profile", thumbnail->import_profile,
"embedded", TRUE,
"intent", thumbnail->intent,
"pcs", VIPS_PCS_XYZ,
NULL ) )
return( -1 );
if( vips_icc_import( in, &t[1],
"input_profile", thumbnail->import_profile,
"embedded", TRUE,
"intent", thumbnail->intent,
"pcs", VIPS_PCS_XYZ,
NULL ) )
return( -1 );
in = t[1];
in = t[1];
have_imported = TRUE;
}
else {
/* Otherwise, use scRGB or GREY16 for linear shrink.
*/
VipsInterpretation interpretation;
have_imported = TRUE;
/* Note the interpretation we will revert to after
* linear.
*/
input_interpretation = in->Type;
if( in->Bands < 3 )
interpretation = VIPS_INTERPRETATION_GREY16;
else
interpretation = VIPS_INTERPRETATION_scRGB;
g_info( "converting to processing space %s",
vips_enum_nick( VIPS_TYPE_INTERPRETATION,
interpretation ) );
if( vips_colourspace( in, &t[2], interpretation,
NULL ) )
return( -1 );
in = t[2];
}
}
else {
/* In non-linear mode, use sRGB or B_W as the processing
* space.
*/
VipsInterpretation interpretation;
/* To the processing colourspace. This will unpack LABQ, import CMYK,
* etc.
*
* If this is a CMYK image, we need to set have_imported since we only
* want to export at the end.
*/
if( in->Type == VIPS_INTERPRETATION_CMYK )
have_imported = TRUE;
if( thumbnail->linear )
interpretation = VIPS_INTERPRETATION_scRGB;
else if( in->Bands < 3 )
interpretation = VIPS_INTERPRETATION_B_W;
else
interpretation = VIPS_INTERPRETATION_sRGB;
g_info( "converting to processing space %s",
vips_enum_nick( VIPS_TYPE_INTERPRETATION, interpretation ) );
if( vips_colourspace( in, &t[2], interpretation, NULL ) )
return( -1 );
in = t[2];
if( in->Bands < 3 )
interpretation = VIPS_INTERPRETATION_B_W;
else
interpretation = VIPS_INTERPRETATION_sRGB;
g_info( "converting to processing space %s",
vips_enum_nick( VIPS_TYPE_INTERPRETATION,
interpretation ) );
if( vips_colourspace( in, &t[2], interpretation,
NULL ) )
return( -1 );
in = t[2];
}
/* Shrink to preshrunk_page_height, so we work for multi-page images.
*/
@ -753,23 +777,23 @@ vips_thumbnail_build( VipsObject *object )
vshrink = (double) in->Ysize / target_image_height;
}
/* vips_premultiply() makes a float image, so when we unpremultiply
* below we must cast back to the original format. Use NOTSET to
* meran no pre/unmultiply.
*/
unpremultiplied_format = VIPS_FORMAT_NOTSET;
/* If there's an alpha, we have to premultiply before shrinking. See
* https://github.com/libvips/libvips/issues/291
*/
have_premultiplied = FALSE;
if( vips_image_hasalpha( in ) &&
hshrink != 1.0 &&
vshrink != 1.0 ) {
g_info( "premultiplying alpha" );
unpremultiplied_format = in->BandFmt;
if( vips_premultiply( in, &t[3], NULL ) )
return( -1 );
have_premultiplied = TRUE;
/* vips_premultiply() makes a float image. When we
* vips_unpremultiply() below, we need to cast back to the
* pre-premultiply format.
*/
unpremultiplied_format = in->BandFmt;
in = t[3];
}
@ -779,6 +803,14 @@ vips_thumbnail_build( VipsObject *object )
return( -1 );
in = t[4];
if( unpremultiplied_format != VIPS_FORMAT_NOTSET ) {
g_info( "unpremultiplying alpha" );
if( vips_unpremultiply( in, &t[5], NULL ) ||
vips_cast( t[5], &t[6], unpremultiplied_format, NULL ) )
return( -1 );
in = t[6];
}
/* Only set page-height if we have more than one page, or this could
* accidentally turn into an animated image later.
*/
@ -794,21 +826,12 @@ vips_thumbnail_build( VipsObject *object )
VIPS_META_PAGE_HEIGHT, output_page_height );
}
if( have_premultiplied ) {
g_info( "unpremultiplying alpha" );
if( vips_unpremultiply( in, &t[5], NULL ) ||
vips_cast( t[5], &t[6], unpremultiplied_format, NULL ) )
return( -1 );
in = t[6];
}
/* Colour management.
*
* If we've already imported, just export. Otherwise, we're in
* device space and we need a combined import/export to transform to
* the target space.
*/
if( have_imported ) {
/* We've already imported, just export. Go to sRGB if there's
* no export profile.
*/
if( thumbnail->export_profile ||
vips_image_get_typeof( in, VIPS_META_ICC_NAME ) ) {
g_info( "exporting to device space with a profile" );
@ -827,21 +850,54 @@ vips_thumbnail_build( VipsObject *object )
in = t[7];
}
}
else if( thumbnail->export_profile &&
(vips_image_get_typeof( in, VIPS_META_ICC_NAME ) ||
thumbnail->import_profile) ) {
else if( thumbnail->export_profile ) {
/* Not imported, but we are doing colour management. Transform
* to the output space.
*/
g_info( "transforming to %s", thumbnail->export_profile );
if( thumbnail->import_profile )
g_info( "fallback input profile %s",
thumbnail->import_profile );
if( vips_icc_transform( in, &t[7],
thumbnail->export_profile,
"input_profile", thumbnail->import_profile,
"intent", thumbnail->intent,
"embedded", TRUE,
NULL ) )
return( -1 );
/* If there's some kind of import profile, we can transform to
* the output. Otherwise we have to convert to PCS and then
* export.
*/
if( thumbnail->import_profile ||
(vips_image_get_typeof( in, VIPS_META_ICC_NAME ) ||
thumbnail->import_profile) ) {
g_info( "transforming with supplied profiles" );
if( vips_icc_transform( in, &t[7],
thumbnail->export_profile,
"input_profile", thumbnail->import_profile,
"intent", thumbnail->intent,
"embedded", TRUE,
NULL ) )
return( -1 );
in = t[7];
}
else {
g_info( "exporting with %s",
thumbnail->export_profile );
if( vips_colourspace( in, &t[7],
VIPS_INTERPRETATION_XYZ, NULL ) ||
vips_icc_export( t[7], &t[8],
"output_profile",
thumbnail->export_profile,
"intent", thumbnail->intent,
NULL ) )
return( -1 );
in = t[8];
}
}
else if( thumbnail->linear ) {
/* Linear mode, no colour management. We went to scRGB for
* processing, so we now revert to the input colourspace.
*/
g_info( "reverting to input space %s",
vips_enum_nick( VIPS_TYPE_INTERPRETATION,
input_interpretation ) );
if( vips_colourspace( in, &t[7],
input_interpretation, NULL ) )
return( -1 );
in = t[7];
}
@ -1370,7 +1426,7 @@ vips_thumbnail_buffer_init( VipsThumbnailBuffer *buffer )
* * @intent: #VipsIntent, rendering intent
* * @option_string: %gchararray, extra loader options
*
* Exacty as vips_thumbnail(), but read from a memory buffer. One extra
* Exactly as vips_thumbnail(), but read from a memory buffer. One extra
* optional argument, @option_string, lets you pass options to the underlying
* loader.
*
@ -1566,7 +1622,7 @@ vips_thumbnail_source_init( VipsThumbnailSource *source )
* * @intent: #VipsIntent, rendering intent
* * @option_string: %gchararray, extra loader options
*
* Exacty as vips_thumbnail(), but read from a source. One extra
* Exactly as vips_thumbnail(), but read from a source. One extra
* optional argument, @option_string, lets you pass options to the underlying
* loader.
*
@ -1673,7 +1729,7 @@ vips_thumbnail_image_init( VipsThumbnailImage *image )
* * @export_profile: %gchararray, export ICC profile
* * @intent: #VipsIntent, rendering intent
*
* Exacty as vips_thumbnail(), but read from an existing image.
* Exactly as vips_thumbnail(), but read from an existing image.
*
* This operation
* is not able to exploit shrink-on-load features of image load libraries, so

2
test/test-suite/helpers/helpers.py
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@ -42,6 +42,8 @@ BMP_FILE = os.path.join(IMAGES, "MARBLES.BMP")
NIFTI_FILE = os.path.join(IMAGES, "avg152T1_LR_nifti.nii.gz")
ICO_FILE = os.path.join(IMAGES, "favicon.ico")
HEIC_FILE = os.path.join(IMAGES, "heic-orientation-6.heic")
RGBA_FILE = os.path.join(IMAGES, "rgba.png")
RGBA_CORRECT_FILE = os.path.join(IMAGES, "rgba-correct.ppm")
MOSAIC_FILES = [os.path.join(IMAGES, "cd1.1.jpg"), os.path.join(IMAGES, "cd1.2.jpg"),
os.path.join(IMAGES, "cd2.1.jpg"), os.path.join(IMAGES, "cd2.2.jpg"),
os.path.join(IMAGES, "cd3.1.jpg"), os.path.join(IMAGES, "cd3.2.jpg"),

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8
test/test-suite/test_resample.py
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@ -2,7 +2,8 @@
import pytest
import pyvips
from helpers import JPEG_FILE, OME_FILE, HEIC_FILE, TIF_FILE, all_formats, have
from helpers import JPEG_FILE, OME_FILE, HEIC_FILE, TIF_FILE, all_formats, \
have, RGBA_FILE, RGBA_CORRECT_FILE
# Run a function expecting a complex image on a two-band image
@ -193,6 +194,11 @@ class TestResample:
im2 = pyvips.Image.thumbnail_buffer(buf, 100)
assert abs(im1.avg() - im2.avg()) < 1
# linear shrink should work on rgba images
im1 = pyvips.Image.thumbnail(RGBA_FILE, 64, linear=True)
im2 = pyvips.Image.new_from_file(RGBA_CORRECT_FILE)
assert abs(im1.flatten(background=255).avg() - im2.avg()) < 1
if have("heifload"):
# this image is orientation 6 ... thumbnail should flip it
im = pyvips.Image.new_from_file(HEIC_FILE)