sergiotarxz/libvips
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add support for palette mono images

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search the colormap for R==G==B and output mono in this case

there is a tiff extension for INDEXED images, but no one seems to use it
This commit is contained in:
John Cupitt 2011-04-21 12:01:37 +01:00
parent 620c02a833
commit e8a78916a3
2 changed files with 41 additions and 8 deletions
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1
ChangeLog
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@ -51,6 +51,7 @@
- got rid of the tools/ subdirs
- added im_bufjpeg2vips()
- tiff reader can do 1, 2, 4, 8 bit palette images
- tiff palette read can do mono images
30/11/10 started 7.24.0
- bump for new stable

48
libvips/format/im_tiff2vips.c
View File

@ -121,6 +121,7 @@
* - argh int/uint mixup for rows_per_strip, thanks Bubba
* 21/4/11
* - palette read can do 1,2,4,8 bits per sample
* - palette read can do mono images
*/
/*
@ -604,6 +605,10 @@ typedef struct {
/* Bits per sample.
*/
int bps;
/* All maps equal, so we write mono.
*/
gboolean mono;
} PaletteRead;
/* Per-scanline process function for palette images.
@ -631,11 +636,16 @@ palette_line( PEL *q, PEL *p, int n, void *flg )
data <<= read->bps;
bit -= read->bps;
q[0] = read->red[i];
q[1] = read->green[i];
q[2] = read->blue[i];
q += 3;
if( read->mono ) {
q[0] = read->red[i];
q += 1;
}
else {
q[0] = read->red[i];
q[1] = read->green[i];
q[2] = read->blue[i];
q += 3;
}
}
}
@ -678,13 +688,35 @@ parse_palette( ReadTiff *rtiff, IMAGE *out )
read->blue[i] = tblue[i] >> 8;
}
out->Bands = 3;
/* Are all the maps equal? We have a mono image.
*/
read->mono = TRUE;
for( i = 0; i < (1 << read->bps); i++ )
if( read->red[i] != read->green[i] ||
read->green[i] != read->blue[i] ) {
read->mono = FALSE;
break;
}
/* There's a TIFF extension, INDEXED, that is the preferred way to
* encode mono palette images, but few applications support it. So we
* just search the colormap.
*/
out->BandFmt = IM_BANDFMT_UCHAR;
out->Coding = IM_CODING_NONE;
out->Type = IM_TYPE_sRGB;
rtiff->sfn = palette_line;
if( read->mono ) {
out->Bands = 1;
out->Type = IM_TYPE_B_W;
}
else {
out->Bands = 3;
out->Type = IM_TYPE_sRGB;
}
rtiff->client = read;
rtiff->sfn = palette_line;
return( 0 );
}