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Improved detection of alpha channel on CMYK images

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This commit is contained in:
Mirco Miranda 2022-06-27 10:04:49 +02:00
parent d4966d169b
commit 3d5090593c
1 changed files with 80 additions and 31 deletions
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111
src/imageformats/psd.cpp
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@ -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);
}
}
}