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PNG: properly handle 1bpp greyscale images with alpha

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PNG allows 1bpp greyscale images (PNG_COLOR_TYPE_GRAY) to have
an alpha key; so even in this case we need to inquiry if
the image has a transparency, and if so modify the color table
of the monochrome image accordingly.

Task-number: QTBUG-33503

Change-Id: Iab07c8f95ac8865269c48816e222645cdcb6bbc1
Reviewed-by: Nicolas Arnaud-Cormos <nicolas@kdab.com>
Reviewed-by: aavit <eirik.aavitsland@digia.com>
This commit is contained in:
Giuseppe D'Angelo 2013-09-17 22:22:30 +02:00 committed by The Qt Project
parent 18a08ab8a1
commit 73b88fcced
1 changed files with 9 additions and 0 deletions
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9
src/gui/image/qpnghandler.cpp
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@ -281,6 +281,15 @@ void setup_qt(QImage& image, png_structp png_ptr, png_infop info_ptr, QSize scal
image.setColorCount(2);
image.setColor(1, qRgb(0,0,0));
image.setColor(0, qRgb(255,255,255));
if (png_get_tRNS(png_ptr, info_ptr, &trans_alpha, &num_trans, &trans_color_p) && trans_color_p) {
const int g = trans_color_p->gray;
// the image has white in the first position of the color table,
// black in the second. g is 0 for black, 1 for white.
if (g == 0)
image.setColor(1, qRgba(0, 0, 0, 0));
else if (g == 1)
image.setColor(0, qRgba(255, 255, 255, 0));
}
} else if (bit_depth == 16 && png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
png_set_expand(png_ptr);
png_set_strip_16(png_ptr);