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Fixes: 32 bit and alpha bmp format image reading

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The bmp handler would ignore the high byte of a 32bit bmp. It
would also ignore any alpha channel.

The actual change is really simple; it just adds the alpha_* members
and the reading of the 4th byte in 32bit depth. However, detection
of alpha channel required switching the order of two independent
blocks of code, hence the size of this patch.

[ChangeLog][QtGui] Support reading bmp images with alpha channel

Task-number: QTBUG-35220
Change-Id: Ib133c3644c03c5cfc728f5fa2c837219804e69ae
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
This commit is contained in:
aavit 2013-12-10 14:39:09 +01:00 committed by The Qt Project
parent cd44f363ff
commit 6f1b82fccd
1 changed files with 61 additions and 46 deletions
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107
src/gui/image/qbmphandler.cpp
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@ -210,54 +210,15 @@ static bool read_dib_body(QDataStream &s, const BMP_INFOHDR &bi, int offset, int
uint red_mask = 0;
uint green_mask = 0;
uint blue_mask = 0;
uint alpha_mask = 0;
int red_shift = 0;
int green_shift = 0;
int blue_shift = 0;
int alpha_shift = 0;
int red_scale = 0;
int green_scale = 0;
int blue_scale = 0;
int ncols = 0;
int depth = 0;
QImage::Format format;
switch (nbits) {
case 32:
case 24:
case 16:
depth = 32;
format = QImage::Format_RGB32;
break;
case 8:
case 4:
depth = 8;
format = QImage::Format_Indexed8;
break;
default:
depth = 1;
format = QImage::Format_Mono;
}
if (bi.biHeight < 0)
h = -h; // support images with negative height
if (image.size() != QSize(w, h) || image.format() != format) {
image = QImage(w, h, format);
if (image.isNull()) // could not create image
return false;
}
if (depth != 32) {
ncols = bi.biClrUsed ? bi.biClrUsed : 1 << nbits;
if (ncols > 256) // sanity check - don't run out of mem if color table is broken
return false;
image.setColorCount(ncols);
}
image.setDotsPerMeterX(bi.biXPelsPerMeter);
image.setDotsPerMeterY(bi.biYPelsPerMeter);
if (!d->isSequential())
d->seek(startpos + BMP_FILEHDR_SIZE + (bi.biSize >= BMP_WIN4? BMP_WIN : bi.biSize)); // goto start of colormap
int alpha_scale = 0;
if (bi.biSize >= BMP_WIN4 || (comp == BMP_BITFIELDS && (nbits == 16 || nbits == 32))) {
if (d->read((char *)&red_mask, sizeof(red_mask)) != sizeof(red_mask))
@ -269,7 +230,6 @@ static bool read_dib_body(QDataStream &s, const BMP_INFOHDR &bi, int offset, int
// Read BMP v4+ header
if (bi.biSize >= BMP_WIN4) {
int alpha_mask = 0;
int CSType = 0;
int gamma_red = 0;
int gamma_green = 0;
@ -307,6 +267,49 @@ static bool read_dib_body(QDataStream &s, const BMP_INFOHDR &bi, int offset, int
}
}
bool transp = (comp == BMP_BITFIELDS) && alpha_mask;
int ncols = 0;
int depth = 0;
QImage::Format format;
switch (nbits) {
case 32:
case 24:
case 16:
depth = 32;
format = transp ? QImage::Format_ARGB32 : QImage::Format_RGB32;
break;
case 8:
case 4:
depth = 8;
format = QImage::Format_Indexed8;
break;
default:
depth = 1;
format = QImage::Format_Mono;
}
if (bi.biHeight < 0)
h = -h; // support images with negative height
if (image.size() != QSize(w, h) || image.format() != format) {
image = QImage(w, h, format);
if (image.isNull()) // could not create image
return false;
}
if (depth != 32) {
ncols = bi.biClrUsed ? bi.biClrUsed : 1 << nbits;
if (ncols > 256) // sanity check - don't run out of mem if color table is broken
return false;
image.setColorCount(ncols);
}
image.setDotsPerMeterX(bi.biXPelsPerMeter);
image.setDotsPerMeterY(bi.biYPelsPerMeter);
if (!d->isSequential())
d->seek(startpos + BMP_FILEHDR_SIZE + (bi.biSize >= BMP_WIN4? BMP_WIN : bi.biSize)); // goto start of colormap
if (ncols > 0) { // read color table
uchar rgb[4];
int rgb_len = t == BMP_OLD ? 3 : 4;
@ -324,6 +327,8 @@ static bool read_dib_body(QDataStream &s, const BMP_INFOHDR &bi, int offset, int
green_scale = 256 / ((green_mask >> green_shift) + 1);
blue_shift = calc_shift(blue_mask);
blue_scale = 256 / ((blue_mask >> blue_shift) + 1);
alpha_shift = calc_shift(alpha_mask);
alpha_scale = 256 / ((alpha_mask >> alpha_shift) + 1);
} else if (comp == BMP_RGB && (nbits == 24 || nbits == 32)) {
blue_mask = 0x000000ff;
green_mask = 0x0000ff00;
@ -344,6 +349,13 @@ static bool read_dib_body(QDataStream &s, const BMP_INFOHDR &bi, int offset, int
blue_scale = 8;
}
#if 0
qDebug("Rmask: %08x Rshift: %08x Rscale:%08x", red_mask, red_shift, red_scale);
qDebug("Gmask: %08x Gshift: %08x Gscale:%08x", green_mask, green_shift, green_scale);
qDebug("Bmask: %08x Bshift: %08x Bscale:%08x", blue_mask, blue_shift, blue_scale);
qDebug("Amask: %08x Ashift: %08x Ascale:%08x", alpha_mask, alpha_shift, alpha_scale);
#endif
// offset can be bogus, be careful
if (offset>=0 && startpos + offset > d->pos()) {
if (!d->isSequential())
@ -535,11 +547,14 @@ static bool read_dib_body(QDataStream &s, const BMP_INFOHDR &bi, int offset, int
b = buf24;
while (p < end) {
c = *(uchar*)b | (*(uchar*)(b+1)<<8);
if (nbits != 16)
if (nbits > 16)
c |= *(uchar*)(b+2)<<16;
*p++ = qRgb(((c & red_mask) >> red_shift) * red_scale,
if (nbits > 24)
c |= *(uchar*)(b+3)<<24;
*p++ = qRgba(((c & red_mask) >> red_shift) * red_scale,
((c & green_mask) >> green_shift) * green_scale,
((c & blue_mask) >> blue_shift) * blue_scale);
((c & blue_mask) >> blue_shift) * blue_scale,
transp ? ((c & alpha_mask) >> alpha_shift) * alpha_scale : 0xff);
b += nbits/8;
}
}