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Improved detection of alpha channels in TIFF images.

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Some TIFF images are not properly formed, for example having an extra channel marked as being unspecified data while they should be treated as being an alpha channel. Detect some of those cases so that these TIFF images now will have alpha.

Applied patch by gmeeker. Closes #12874.



git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66717 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Dimitri Schoolwerth
2011-01-19 13:47:18 +00:00
parent 77b83d0a0f
commit 3d59540f87
1 changed files with 13 additions and 3 deletions
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16
src/common/imagtiff.cpp
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@@ -296,13 +296,23 @@ bool wxTIFFHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbos
TIFFGetField( tif, TIFFTAG_IMAGEWIDTH, &w );
TIFFGetField( tif, TIFFTAG_IMAGELENGTH, &h );
uint16 photometric;
uint16 samplesPerPixel;
uint16 extraSamples;
uint16* samplesInfo;
TIFFGetFieldDefaulted(tif, TIFFTAG_SAMPLESPERPIXEL, &samplesPerPixel);
TIFFGetFieldDefaulted(tif, TIFFTAG_EXTRASAMPLES,
&extraSamples, &samplesInfo);
const bool hasAlpha = (extraSamples == 1 &&
(samplesInfo[0] == EXTRASAMPLE_ASSOCALPHA ||
samplesInfo[0] == EXTRASAMPLE_UNASSALPHA));
if (!TIFFGetField(tif, TIFFTAG_PHOTOMETRIC, &photometric))
{
photometric = PHOTOMETRIC_MINISWHITE;
}
const bool hasAlpha = (extraSamples >= 1
&& ((samplesInfo[0] == EXTRASAMPLE_UNSPECIFIED && samplesPerPixel > 3)
|| samplesInfo[0] == EXTRASAMPLE_ASSOCALPHA
|| samplesInfo[0] == EXTRASAMPLE_UNASSALPHA))
|| (extraSamples == 0 && samplesPerPixel == 4
&& photometric == PHOTOMETRIC_RGB);
// guard against integer overflow during multiplication which could result
// in allocating a too small buffer and then overflowing it