PSD: add support for GrayA (8/16/32 bit) and Gray 32 bit

README.md

@@ -414,6 +414,8 @@ PSD support has the following limitations:
 - Multichannel images are treated as CMYK if they have 2 or more channels.
 - Multichannel images are treated as Grayscale if they have 1 channel.
 - Duotone images are treated as grayscale images.
+- Grayscale images with alpha channel or at 32 bit depth are converted to 
+  RGBA due to the lack of the appropriate Qt grayscale container.
 - Extra channels other than alpha are discarded.
 
 The following defines can be defined in cmake to modify the behavior of the 

autotests/read/psd/32bit_grayscale.psd.json

@@ -2,8 +2,8 @@
     {
         "fileName" : "32bit_grayscale.png",
         "colorSpace" : {
-            "description" : "Linear Grayscale Profile",
-            "colorModel" : "Gray",
+            "description" : "RGB emulation of \"Linear Grayscale Profile\"",
+            "colorModel" : "Rgb",
             "primaries" : "Custom",
             "transferFunction" : "Linear",
             "gamma" : 1

autotests/read/psd/testcard_graya16.psd.json

@@ -0,0 +1,26 @@
+[
+    {
+        "fileName" : "testcard_graya16.png",
+        "colorSpace" : {
+            "description" : "RGB emulation of \"Gray Gamma 2.2\"",
+            "colorModel" : "Rgb",
+            "primaries" : "SRgb",
+            "transferFunction" : "Gamma",
+            "gamma" : 2.19922
+        },
+        "metadata" : [
+            {
+                "key" : "ModificationDate",
+                "value" : "2025-11-17T07:27:47"
+            },
+            {
+                "key" : "Software" ,
+                "value" : "Adobe Photoshop 26.11 (Windows)"
+            }
+        ],
+        "resolution" : {
+            "dotsPerMeterX" : 11811,
+            "dotsPerMeterY" : 11811
+        }
+    }
+]

autotests/read/psd/testcard_graya32.psd.json

@@ -0,0 +1,26 @@
+[
+    {
+        "fileName" : "testcard_graya32.png",
+        "colorSpace" : {
+            "description" : "RGB emulation of \"Profilo scala di grigio lineare\"",
+            "colorModel" : "Rgb",
+            "primaries" : "Custom",
+            "transferFunction" : "Linear",
+            "gamma" : 1
+        },
+        "metadata" : [
+            {
+                "key" : "ModificationDate",
+                "value" : "2025-11-17T07:29:19"
+            },
+            {
+                "key" : "Software" ,
+                "value" : "Adobe Photoshop 26.11 (Windows)"
+            }
+        ],
+        "resolution" : {
+            "dotsPerMeterX" : 11811,
+            "dotsPerMeterY" : 11811
+        }
+    }
+]

autotests/read/psd/testcard_graya8.psd.json

@@ -0,0 +1,28 @@
+[
+    {
+        "fileName" : "testcard_graya8.png",
+        "fuzziness" : 1,
+        "perceptiveFuzziness" : true,
+        "colorSpace" : {
+            "description" : "RGB emulation of \"Gray Gamma 2.2\"",
+            "colorModel" : "Rgb",
+            "primaries" : "SRgb",
+            "transferFunction" : "Gamma",
+            "gamma" : 2.19922
+        },
+        "metadata" : [
+            {
+                "key" : "ModificationDate",
+                "value" : "2025-11-17T07:28:50"
+            },
+            {
+                "key" : "Software" ,
+                "value" : "Adobe Photoshop 26.11 (Windows)"
+            }
+        ],
+        "resolution" : {
+            "dotsPerMeterX" : 11811,
+            "dotsPerMeterY" : 11811
+        }
+    }
+]

src/imageformats/psd.cpp

@@ -546,8 +546,21 @@ static bool setColorSpace(QImage &img, const PSDImageResourceSection &irs)
     auto cs = QColorSpace::fromIccProfile(irb.data);
     if (!cs.isValid())
         return false;
+
+    if (cs.colorModel() == QColorSpace::ColorModel::Gray && img.pixelFormat().colorModel() != QPixelFormat::Grayscale) {
+        // I created an RGB from a grayscale without using color profile conversion (fast).
+        // I'll try to create an RGB profile that looks the same.
+        if (cs.transferFunction() != QColorSpace::TransferFunction::Custom) {
+            auto tmp = QColorSpace(QColorSpace::Primaries::SRgb, cs.transferFunction(), cs.gamma());
+            tmp.setWhitePoint(cs.whitePoint());
+            tmp.setDescription(QStringLiteral("RGB emulation of \"%1\"").arg(cs.description()));
+            if (tmp.isValid())
+                cs = tmp;
+        }
+    }
+
     img.setColorSpace(cs);
-    return true;
+    return img.colorSpace().isValid();
 }
 
 /*!
@@ -800,6 +813,14 @@ static QImage::Format imageFormat(const PSDHeader &header, bool alpha)
         }
         break;
     case CM_GRAYSCALE:
+        if (header.depth == 32) {
+            format = !alpha ? QImage::Format_RGBX32FPx4 : QImage::Format_RGBA32FPx4_Premultiplied;
+        } else if (header.depth == 16) {
+            format = !alpha ? QImage::Format_Grayscale16 : QImage::Format_RGBA64_Premultiplied;
+        } else {
+            format = !alpha ? QImage::Format_Grayscale8 : QImage::Format_RGBA8888_Premultiplied;
+        }
+        break;
     case CM_DUOTONE:
         format = header.depth == 8 ? QImage::Format_Grayscale8 : QImage::Format_Grayscale16;
         break;
@@ -1309,7 +1330,6 @@ bool PSDHandler::read(QImage *image)
     }
 
     auto imgChannels = imageChannels(img.format());
-    auto channel_num = std::min(qint32(header.channel_count), imgChannels);
     auto raw_count = qsizetype(header.width * header.depth + 7) / 8;
     auto native_cmyk = img.format() == CMYK_FORMAT;
 
@@ -1417,6 +1437,14 @@ bool PSDHandler::read(QImage *image)
                     else if (header.depth == 32)
                         premulConversion<float>(scanLine, header.width, 3, header.channel_count, PremulConversion::PS2P);
                 }
+                if (header.color_mode == CM_GRAYSCALE) {
+                    if (header.depth == 8)
+                        premulConversion<quint8>(scanLine, header.width, 1, header.channel_count, PremulConversion::PS2P);
+                    else if (header.depth == 16)
+                        premulConversion<quint16>(scanLine, header.width, 1, header.channel_count, PremulConversion::PS2P);
+                    else if (header.depth == 32)
+                        premulConversion<float>(scanLine, header.width, 1, header.channel_count, PremulConversion::PS2P);
+                }
             }
 
             // Conversion to RGB
@@ -1454,9 +1482,21 @@ bool PSDHandler::read(QImage *image)
                 else if (header.depth == 32)
                     rawChannelsCopy<float>(img.scanLine(y), imgChannels, psdScanline.data(), header.channel_count, header.width);
             }
+            if (header.color_mode == CM_GRAYSCALE) {
+                for (auto c = 0; c < imgChannels; ++c) { // GRAYA to RGBA
+                    auto sc = qBound(0, c - 2, int(header.channel_count));
+                    if (header.depth == 8)
+                        rawChannelCopy<quint8>(img.scanLine(y), imgChannels, c, psdScanline.data(), header.channel_count, sc, header.width);
+                    else if (header.depth == 16)
+                        rawChannelCopy<quint16>(img.scanLine(y), imgChannels, c, psdScanline.data(), header.channel_count, sc, header.width);
+                    else if (header.depth == 32)
+                        rawChannelCopy<float>(img.scanLine(y), imgChannels, c, psdScanline.data(), header.channel_count, sc, header.width);
+                }
+            }
         }
     } else {
         // Linear read (no position jumps): optimized code usable only for the colorspaces supported by QImage
+        auto channel_num = std::min(qint32(header.channel_count), header.color_mode == CM_GRAYSCALE ? 1 : imgChannels);
         for (qint32 c = 0; c < channel_num; ++c) {
             for (qint32 y = 0, h = header.height; y < h; ++y) {
                 auto&& strideSize = strides.at(c * qsizetype(h) + y);
@@ -1485,8 +1525,13 @@ bool PSDHandler::read(QImage *image)
                     // 32-bits float images: RGB/RGBA
                     planarToChunchy<float>(scanLine, rawStride.data(), header.width, c, imgChannels);
                 } else if (header.depth == 32 && header.color_mode == CM_GRAYSCALE) {
-                    // 32-bits float images: Grayscale (coverted to equivalent integer 16-bits)
-                    planarToChunchyFloatToUInt16<float>(scanLine, rawStride.data(), header.width, c, imgChannels);
+                    if (imgChannels >= 3) { // GRAY to RGB
+                        planarToChunchy<float>(scanLine, rawStride.data(), header.width, 0, imgChannels);
+                        planarToChunchy<float>(scanLine, rawStride.data(), header.width, 1, imgChannels);
+                        planarToChunchy<float>(scanLine, rawStride.data(), header.width, 2, imgChannels);
+                    } else { // 32-bits float images: Grayscale (coverted to equivalent integer 16-bits)
+                        planarToChunchyFloatToUInt16<float>(scanLine, rawStride.data(), header.width, c, imgChannels);
+                    }
                 }
             }
         }
@@ -1622,6 +1667,9 @@ bool PSDHandler::canRead(QIODevice *device)
         if (header.color_mode == CM_RGB && header.channel_count > 3) {
             return false; // supposing extra channel as alpha
         }
+        if (header.color_mode == CM_GRAYSCALE && (header.channel_count > 1 || header.depth == 32)) {
+            return false; // supposing extra channel as alpha
+        }
     }
 
     return IsSupported(header);