From 3d5090593c7cfd62d65e66a9caacf8780be63da7 Mon Sep 17 00:00:00 2001
From: Mirco Miranda <mirco.miranda@systemceramics.com>
Date: Mon, 27 Jun 2022 10:04:49 +0200
Subject: [PATCH] Improved detection of alpha channel on CMYK images
---
src/imageformats/psd.cpp | 111 ++++++++++++++++++++++++++++-----------
1 file changed, 80 insertions(+), 31 deletions(-)
diff --git a/src/imageformats/psd.cpp b/src/imageformats/psd.cpp
index 5f13481..794758e 100644
--- a/src/imageformats/psd.cpp
+++ b/src/imageformats/psd.cpp
@@ -101,6 +101,10 @@ struct PSDColorModeDataSection {
using PSDImageResourceSection = QHash<quint16, PSDImageResourceBlock>;
+struct PSDLayerAndMaskSection {
+ qint16 layerCount = 0;
+};
+
/*!
* \brief fixedPointToDouble
* Converts a fixed point number to floating point one.
@@ -112,6 +116,28 @@ static double fixedPointToDouble(qint32 fixedPoint)
return (i+d);
}
+static bool skip_section(QDataStream &s, bool psb = false)
+{
+ qint64 section_length;
+ if (!psb) {
+ quint32 tmp;
+ s >> tmp;
+ section_length = tmp;
+ }
+ else {
+ s >> section_length;
+ }
+
+ // Skip mode data.
+ for (qint32 i32 = 0; section_length; section_length -= i32) {
+ i32 = std::min(section_length, qint64(std::numeric_limits<qint32>::max()));
+ i32 = s.skipRawData(i32);
+ if (i32 < 1)
+ return false;
+ }
+ return true;
+}
+
/*!
* \brief readPascalString
* Reads the Pascal string as defined in the PSD specification.
@@ -250,6 +276,46 @@ static PSDImageResourceSection readImageResourceSection(QDataStream &s, bool *ok
return irs;
}
+
+PSDLayerAndMaskSection readLayerAndMaskSection(QDataStream &s, bool isPsb, bool *ok = nullptr)
+{
+ PSDLayerAndMaskSection lms;
+
+ bool tmp = true;
+ if (ok == nullptr)
+ ok = &tmp;
+ *ok = true;
+
+ // try to read layerCount: if less than zero, means that there is an alpha channel
+ if (auto device = s.device()) {
+ device->startTransaction();
+ qint64 size = 0;
+ if (isPsb) {
+ qint64 tmpSize;
+ s >> tmpSize; // global size
+ if (tmpSize >= 8)
+ s >> size; // layer info size
+ }
+ else {
+ quint32 tmpSize;
+ s >> tmpSize; // global size
+ if (tmpSize >= 4) {
+ s >> tmpSize; // layer info size
+ size = tmpSize;
+ }
+ }
+
+ if (s.status() == QDataStream::Ok) {
+ if (size >= 2)
+ s >> lms.layerCount;
+ }
+ device->rollbackTransaction();
+ }
+
+ *ok = skip_section(s, isPsb);
+ return lms;
+}
+
/*!
* \brief readColorModeDataSection
* Read the color mode section
@@ -456,28 +522,6 @@ static bool IsSupported(const PSDHeader &header)
return true;
}
-static bool skip_section(QDataStream &s, bool psb = false)
-{
- qint64 section_length;
- if (!psb) {
- quint32 tmp;
- s >> tmp;
- section_length = tmp;
- }
- else {
- s >> section_length;
- }
-
- // Skip mode data.
- for (qint32 i32 = 0; section_length; section_length -= i32) {
- i32 = std::min(section_length, qint64(std::numeric_limits<qint32>::max()));
- i32 = s.skipRawData(i32);
- if (i32 < 1)
- return false;
- }
- return true;
-}
-
/*!
* \brief decompress
* Fast PackBits decompression.
@@ -526,7 +570,7 @@ qint64 decompress(const char *input, qint64 ilen, char *output, qint64 olen)
* \param header The PSD header.
* \return The Qt image format.
*/
-static QImage::Format imageFormat(const PSDHeader &header)
+static QImage::Format imageFormat(const PSDHeader &header, qint32 alpha)
{
if (header.channel_count == 0) {
return QImage::Format_Invalid;
@@ -542,9 +586,9 @@ static QImage::Format imageFormat(const PSDHeader &header)
break;
case CM_CMYK: // PSD supports CMYK 8-bits and 16-bits only
if (header.depth == 16)
- format = header.channel_count < 5 ? QImage::Format_RGBX64 : QImage::Format_RGBA64;
+ format = header.channel_count < 5 || alpha >= 0 ? QImage::Format_RGBX64 : QImage::Format_RGBA64;
else if (header.depth == 8)
- format = header.channel_count < 5 ? QImage::Format_RGB888 : QImage::Format_RGBA8888;
+ format = header.channel_count < 5 || alpha >= 0 ? QImage::Format_RGB888 : QImage::Format_RGBA8888;
break;
case CM_GRAYSCALE:
case CM_DUOTONE:
@@ -644,7 +688,7 @@ inline void monoInvert(uchar *target, const char* source, qint32 bytes)
}
template<class T>
-inline void cmykToRgb(uchar *target, qint32 targetChannels, const char *source, qint32 sourceChannels, qint32 width)
+inline void cmykToRgb(uchar *target, qint32 targetChannels, const char *source, qint32 sourceChannels, qint32 width, bool noAlpha)
{
auto s = reinterpret_cast<const T*>(source);
auto t = reinterpret_cast<T*>(target);
@@ -667,7 +711,7 @@ inline void cmykToRgb(uchar *target, qint32 targetChannels, const char *source,
*(pt + 1) = T(std::min(max - (M * (1 - K) + K) * max + 0.5, max));
*(pt + 2) = T(std::min(max - (Y * (1 - K) + K) * max + 0.5, max));
if (targetChannels == 4) {
- if (sourceChannels == 5)
+ if (sourceChannels >= 5 && !noAlpha)
*(pt + 3) = *(ps + 4);
else
*(pt + 3) = std::numeric_limits<T>::max();
@@ -721,7 +765,8 @@ static bool LoadPSD(QDataStream &stream, const PSDHeader &header, QImage &img)
}
// Layer and Mask section
- if (!skip_section(stream, isPsb)) {
+ auto lms = readLayerAndMaskSection(stream, isPsb, &ok);
+ if (!ok) {
qDebug() << "Error while skipping Layer and Mask section";
return false;
}
@@ -737,7 +782,11 @@ static bool LoadPSD(QDataStream &stream, const PSDHeader &header, QImage &img)
return false;
}
- const QImage::Format format = imageFormat(header);
+ // 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
+ auto alpha = lms.layerCount; // < 0 alpha present, > 0 spots are not alpha, 0 does not decide
+
+ const QImage::Format format = imageFormat(header, alpha);
if (format == QImage::Format_Invalid) {
qWarning() << "Unsupported image format. color_mode:" << header.color_mode << "depth:" << header.depth << "channel_count:" << header.channel_count;
return false;
@@ -828,9 +877,9 @@ static bool LoadPSD(QDataStream &stream, const PSDHeader &header, QImage &img)
// Conversion to RGB
if (header.color_mode == CM_CMYK) {
if (header.depth == 8)
- cmykToRgb<quint8>(img.scanLine(y), imgChannels, psdScanline.data(), header.channel_count, header.width);
+ cmykToRgb<quint8>(img.scanLine(y), imgChannels, psdScanline.data(), header.channel_count, header.width, alpha >= 0);
else
- cmykToRgb<quint16>(img.scanLine(y), imgChannels, psdScanline.data(), header.channel_count, header.width);
+ cmykToRgb<quint16>(img.scanLine(y), imgChannels, psdScanline.data(), header.channel_count, header.width, alpha >= 0);
}
}
}