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better thumbnailing of multipage docs

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shrink-on-load should now work for multipage PDF thumbnailing

see https://github.com/libvips/libvips/issues/1297
This commit is contained in:
John Cupitt 2019-04-29 17:05:19 +01:00
parent 8482aa3ff1
commit 522ddc1430
1 changed files with 43 additions and 28 deletions
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71
libvips/resample/thumbnail.c
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@ -109,17 +109,16 @@ typedef struct _VipsThumbnail {
int input_height;
int page_height;
VipsAngle angle; /* From vips_autorot_get_angle() */
int n_pages; /* Pages in this image, not original */
/* For openslide, we need to read out the size of each level too.
*
* These are filled out for pyr tiffs as well.
*/
int level_count;
int level_width[MAX_LEVELS];
int level_height[MAX_LEVELS];
/* Try to get n-pages too, for pyr tiff load.
*/
int n_pages;
/* For HEIF, try to fetch the size of the stored thumbnail.
*/
int heif_thumbnail_width;
@ -191,14 +190,16 @@ vips_thumbnail_read_header( VipsThumbnail *thumbnail, VipsImage *image )
thumbnail->input_width = image->Xsize;
thumbnail->input_height = image->Ysize;
thumbnail->angle = vips_autorot_get_angle( image );
thumbnail->page_height = vips_image_get_page_height( image );
if( vips_image_get_typeof( image, VIPS_META_N_PAGES ) ) {
int n_pages;
if( !vips_image_get_int( image, VIPS_META_N_PAGES, &n_pages ) )
thumbnail->n_pages =
VIPS_CLIP( 1, n_pages, MAX_LEVELS );
}
/* The "n-pages" metadata item is the number of pages in the document,
* not the number we've read out into this image. We calculate
* ourselves from page_height.
*
* vips_image_get_page_height() verifies that Ysize is a simple
* multiple pof page_height.
*/
thumbnail->n_pages = thumbnail->input_height / thumbnail->page_height;
/* For openslide, read out the level structure too.
*/
@ -255,7 +256,7 @@ vips_thumbnail_get_tiff_pyramid( VipsThumbnail *thumbnail )
expected_level_width = thumbnail->input_width / (1 << i);
expected_level_height = thumbnail->input_height / (1 << i);
/* Won't be exact due to rounding etc.
/* This won't be exact due to rounding etc.
*/
if( abs( level_width - expected_level_width ) > 5 ||
level_width < 2 )
@ -408,7 +409,7 @@ vips_thumbnail_find_jpegshrink( VipsThumbnail *thumbnail,
return( 1 );
}
/* Find the best openslide level.
/* Find the best pyramid (openslide or tiff) level.
*/
static int
vips_thumbnail_find_pyrlevel( VipsThumbnail *thumbnail,
@ -447,7 +448,7 @@ vips_thumbnail_open( VipsThumbnail *thumbnail )
g_info( "input size is %d x %d",
thumbnail->input_width, thumbnail->input_height );
/* For tiff, we need to make a separate get_info() for each page to
/* For tiff, we need a separate ->open() for each page to
* get all the pyramid levels.
*/
if( vips_isprefix( "VipsForeignLoadTiff", thumbnail->loader ) )
@ -459,6 +460,10 @@ vips_thumbnail_open( VipsThumbnail *thumbnail )
if( vips_isprefix( "VipsForeignLoadHeif", thumbnail->loader ) )
vips_thumbnail_get_heif_thumb_info( thumbnail );
/* We read the openslide level structure in
* vips_thumbnail_read_header().
*/
factor = 1.0;
if( vips_isprefix( "VipsForeignLoadJpeg", thumbnail->loader ) ) {
@ -468,20 +473,28 @@ vips_thumbnail_open( VipsThumbnail *thumbnail )
g_info( "loading jpeg with factor %g pre-shrink", factor );
}
else if( vips_isprefix( "VipsForeignLoadTiff", thumbnail->loader ) ||
vips_isprefix( "VipsForeignLoadOpenslide", thumbnail->loader ) ) {
vips_isprefix( "VipsForeignLoadOpenslide",
thumbnail->loader ) ) {
factor = vips_thumbnail_find_pyrlevel( thumbnail,
thumbnail->input_width, thumbnail->input_height );
g_info( "loading pyr level %g", factor );
}
else if( vips_isprefix( "VipsForeignLoadPdf", thumbnail->loader ) ||
vips_isprefix( "VipsForeignLoadSvg", thumbnail->loader ) ) {
else if( vips_isprefix( "VipsForeignLoadPdf", thumbnail->loader ) ) {
factor = 1.0 /
vips_thumbnail_calculate_common_shrink( thumbnail,
thumbnail->input_width,
thumbnail->page_height );
g_info( "loading PDF with factor %g pre-scale", factor );
}
else if( vips_isprefix( "VipsForeignLoadSvg", thumbnail->loader ) ) {
factor = 1.0 /
vips_thumbnail_calculate_common_shrink( thumbnail,
thumbnail->input_width,
thumbnail->input_height );
g_info( "loading PDF/SVG with factor %g pre-scale", factor );
g_info( "loading SVG with factor %g pre-scale", factor );
}
else if( vips_isprefix( "VipsForeignLoadHeif", thumbnail->loader ) ) {
/* 'factor' is a gboolean which enables thumbnail load instead
@ -532,6 +545,8 @@ vips_thumbnail_build( VipsObject *object )
VIPS_INTERPRETATION_scRGB : VIPS_INTERPRETATION_sRGB;
VipsImage *in;
int preshrunk_page_height;
int output_page_height;
double hshrink;
double vshrink;
@ -572,10 +587,9 @@ vips_thumbnail_build( VipsObject *object )
return( -1 );
in = t[0];
/* So page_height is after pre-shrink, but before the main shrink
* stage.
/* After pre-shrink, but before the main shrink stage.
*/
thumbnail->page_height = vips_image_get_page_height( in );
preshrunk_page_height = vips_image_get_page_height( in );
/* RAD needs special unpacking.
*/
@ -656,17 +670,17 @@ vips_thumbnail_build( VipsObject *object )
in = t[3];
}
/* Shrink to page_height, so we work for multi-page images.
/* Shrink to preshrunk_page_height, so we work for multi-page images.
*/
vips_thumbnail_calculate_shrink( thumbnail,
in->Xsize, thumbnail->page_height, &hshrink, &vshrink );
in->Xsize, preshrunk_page_height, &hshrink, &vshrink );
/* In toilet-roll mode, we must adjust vshrink so that we exactly hit
* page_height or we'll have pixels straddling pixel boundaries.
* page_height or we'll have pixels straddling page boundaries.
*/
if( in->Ysize > thumbnail->page_height ) {
if( in->Ysize > preshrunk_page_height ) {
int target_page_height = VIPS_RINT(
thumbnail->page_height / vshrink );
preshrunk_page_height / vshrink );
int target_image_height = target_page_height *
thumbnail->n_pages;
@ -679,8 +693,9 @@ vips_thumbnail_build( VipsObject *object )
return( -1 );
in = t[4];
thumbnail->page_height = VIPS_RINT( thumbnail->page_height / vshrink );
vips_image_set_int( in, VIPS_META_PAGE_HEIGHT, thumbnail->page_height );
output_page_height = VIPS_RINT( preshrunk_page_height / vshrink );
vips_image_set_int( in,
VIPS_META_PAGE_HEIGHT, output_page_height );
if( have_premultiplied ) {
g_info( "unpremultiplying alpha" );