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PSD: Alpha detection improvements

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Small fix to improve alpha detection by checking also the Alpha Identifiers.
This commit is contained in:
Mirco Miranda 2025-01-20 22:30:23 +00:00 committed by Albert Astals Cid
parent baaf1093a1
commit be534ea06e
1 changed files with 26 additions and 4 deletions
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30
src/imageformats/psd.cpp
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@ -56,13 +56,21 @@ typedef quint8 uchar;
*/
// #define PSD_FAST_LAB_CONVERSION
/*
* Since Qt version 6.8, the 8-bit CMYK format is natively supported.
/* Since Qt version 6.8, the 8-bit CMYK format is natively supported.
* If you encounter problems with native CMYK support you can continue to force the plugin to convert
* to RGB as in previous versions by defining PSD_NATIVE_CMYK_SUPPORT_DISABLED.
*/
// #define PSD_NATIVE_CMYK_SUPPORT_DISABLED
/* The detection of the nature of the extra channel (alpha or not) passes through the reading of
* the PSD sections.
* By default, any extra channel is assumed to be non-alpha. If enabled, for RGB images only,
* any extra channel is assumed as alpha unless refuted by the data in the various sections.
*
* Note: this parameter is for debugging only and should not be enabled in releases.
*/
// #define PSD_FORCE_RGBA
namespace // Private.
{
@ -96,6 +104,7 @@ enum ImageResourceId : quint16 {
IRI_RESOLUTIONINFO = 0x03ED,
IRI_ICCPROFILE = 0x040F,
IRI_TRANSPARENCYINDEX = 0x0417,
IRI_ALPHAIDENTIFIERS = 0x041D,
IRI_VERSIONINFO = 0x0421,
IRI_EXIFDATA1 = 0x0422,
IRI_EXIFDATA3 = 0x0423, // never seen
@ -1134,9 +1143,23 @@ public:
{
// Try to identify the nature of spots: note that this is just one of many ways to identify the presence
// of alpha channels: should work in most cases where colorspaces != RGB/Gray
#ifdef PSD_FORCE_RGBA
auto alpha = m_header.color_mode == CM_RGB;
if (!m_lms.isNull())
#else
auto alpha = false;
#endif
if (m_irs.contains(IRI_ALPHAIDENTIFIERS)) {
auto irb = m_irs.value(IRI_ALPHAIDENTIFIERS);
if (irb.data.size() >= 4) {
QDataStream s(irb.data);
s.setByteOrder(QDataStream::BigEndian);
qint32 v;
s >> v;
alpha = v == 0;
}
} else if (!m_lms.isNull()) {
alpha = m_lms.hasAlpha();
}
return alpha;
}
@ -1164,7 +1187,6 @@ public:
bool readInfo(QDataStream &stream)
{
// Checking for PSB
auto ok = false;
// Header