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Save grayscale palleted images to grayscale png

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While Qt does not support grayscale images explicitly it makes sense to
save palleted images to grayscale png when possible for better
compression and compatibility as opening and saving grayscale images now
converts them to palleted

Change-Id: Iab7c5a5a9d24b9352f5a7bafe04824a97d2463d9
Reviewed-by: aavit <eirik.aavitsland@digia.com>
This commit is contained in:
Sergey Borovkov 2012-10-27 18:17:05 +04:00 committed by The Qt Project
parent 0d519164f2
commit b009ed0cc8
1 changed files with 7 additions and 4 deletions
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11
src/gui/image/qpnghandler.cpp
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@ -102,7 +102,6 @@ QT_BEGIN_NAMESPACE
All PNG files load to the minimal QImage equivalent.
All QImage formats output to reasonably efficient PNG equivalents.
Never to grayscale.
*/
class QPngHandlerPrivate
@ -834,8 +833,12 @@ bool Q_INTERNAL_WIN_NO_THROW QPNGImageWriter::writeImage(const QImage& image, vo
int color_type = 0;
if (image.colorCount())
color_type = PNG_COLOR_TYPE_PALETTE;
if (image.colorCount()) {
if (image.isGrayscale())
color_type = PNG_COLOR_TYPE_GRAY;
else
color_type = PNG_COLOR_TYPE_PALETTE;
}
else if (image.hasAlphaChannel())
color_type = PNG_COLOR_TYPE_RGB_ALPHA;
else
@ -852,7 +855,7 @@ bool Q_INTERNAL_WIN_NO_THROW QPNGImageWriter::writeImage(const QImage& image, vo
if (image.format() == QImage::Format_MonoLSB)
png_set_packswap(png_ptr);
if (image.colorCount()) {
if (color_type == PNG_COLOR_TYPE_PALETTE) {
// Paletted
int num_palette = qMin(256, image.colorCount());
png_color palette[256];