TGA: Support for TGA specification 2.0

Adds TGA 2.0 compliance:
- Support for Extension Area, Developer Area and Footer (metadata support)
- Support for 15-bit and 16-bit per pixel images (both RGB and Indexed)
- Full support for rotation on reading (we cannot use Qt transformations because only a subset is part of the TGA specification)
- When writing you can choose the supported version (subType)
- Improved writing speed (approximately 10 times) and removed whole image conversions (significant memory savings)

It pass the [TrueVision TGA 2.0 conformance suite](https://github.com/zigimg/test-suite/tree/master/fixtures/tga).

Test changes:
- Read test: added ability to skip a specific test on sequential devices (via JSON behavior file)
- Write test: added the ability to set the subType when writing (via JSON properties file)

Closes #37

README.md

@@ -56,11 +56,17 @@ submit the plugin directly to the Qt Project.
 To be accepted, contributions must:
 - Contain the test images needed to verify that the changes work correctly.
 - Pass the tests successfully.
+- Use Qt logging categories for Debug messages.
 
 For more info about tests, see also [Autotests README](autotests/README.md).
 
 ## Duplicated Plugins
 
+> [!important]
+> To ensure you are using the correct plugin, the unwanted one should be 
+renamed or deleted. If several plugins support the same capability, Qt will 
+select one arbitrarily.
+
 ### The TGA plugin
 
 The TGA plugin supports more formats than Qt's own TGA plugin;
@@ -340,10 +346,6 @@ The plugin supports the following image data:
 - FOR4 CIMG (Maya Image File Format): It supports 24/48-bit RGB and 32/64-bit 
   RGBA images.
 
-The plugin does not load images with non-standard SHAM/CTBL chunks due to the
-lack of clear specifications.
-
-
 ### The JP2 plugin
 
 **This plugin can be disabled by setting `KIMAGEFORMATS_JP2` to `OFF` 
@@ -426,6 +428,25 @@ selectively change the conversion (see also [raw_p.h](./src/imageformats/raw_p.h
 
 The default setting tries to balance quality and conversion speed.
 
+### The TGA plugin
+
+TGA plugin supports both version 1 and version 2 of TGA files. When writing,
+it is possible to force which version to use by setting the following subtypes:
+- `TGAv1`: force TGA v1.0. No metadata.
+- `TGAv2` (default): force TGA v2.0 (strict). Adds the TGA Extension Area.
+- `TGAv2E`: force TGA v2.0 (enhanced). Same as TGA v2.0 (strict) but with the 
+  addition of the TGA v2.0 Developer Area with info like, for e.g., Exif data, 
+  XMP packet and the ICC profile.
+
+They are all TGA specs compliant. While for versions 1 and 2 (strict) it is 
+possible to decode all the information with the TGA specification alone, for 
+version 2 (enhanced) it is necessary to know how the additional data is
+encoded.
+
+The following defines can be defined in cmake to modify the behavior of the 
+plugin:
+- `TGA_V2E_AS_DEFAULT`: change the default version of the plugin to `TGAv2E`.
+
 ### The XCF plugin
 
 XCF support has the following limitations:

autotests/CMakeLists.txt

@@ -189,7 +189,7 @@ kimageformats_write_tests(
     pic-lossless
     qoi-lossless
     rgb-lossless
-    tga # fixme: the alpha images appear not to be written properly
+    tga-nodatacheck
 )
 
 # EPS read tests depend on the vagaries of GhostScript

autotests/README.md

@@ -88,30 +88,33 @@ are iterated sequentially and the first object that matches the requirements
 is used for testing (successes are ignored).
 
 Supported values ​​for JSON objects:
-- `comment`: Type string. A string shown by the test when a condition occurs.
-- `description`: Type string. A description of the object. Not used by the 
+- `comment`: Type `string`. A string shown by the test when a condition occurs.
+- `description`: Type `string`. A description of the object. Not used by the 
 test.
-- `disableAutoTransform`: Type boolean. By default, tests are run with 
+- `disableAutoTransform`: Type `boolean`. By default, tests are run with 
 autotransform enabled (i.e. rotation is applied if the plugin supports it).
 Set to `true` to disable autotransform.
-- `filename`: Type string. Name of the template file to use. E.g. 
+- `filename`: Type `string`. Name of the template file to use. E.g. 
 "testRGB_Qt_6_2.png".
-- `fuzziness`: Type integer. Set the fuzziness only if not already set on the 
+- `fuzziness`: Type `integer`. Set the fuzziness only if not already set on the 
 command line. The value set on the command line wins over the one in the JSON 
 file.
-- `maxQtVersion`: Type string. Maximum Qt version this object is compatible 
+- `maxQtVersion`: Type `string`. Maximum Qt version this object is compatible 
 with (if not set means all). E.g. "6.2.99".
-- `metadata`: Type Array. An array of key/value objects (string type) 
+- `metadata`: Type `array`. An array of key/value objects (string type) 
 containing the image metadata as returned by `QImage::text`.
-- `minQtVersion`: Type string. Minimum Qt version this object is compatible 
+- `minQtVersion`: Type `string`. Minimum Qt version this object is compatible 
 with (if not set means all). E.g. "6.2.0".
-- `perceptiveFuzziness` Type boolean. Set the perceptive fuzziness only if not
+- `perceptiveFuzziness` Type `boolean`. Set the perceptive fuzziness only if not
 already set on the command line. The value set on the command line wins over 
 the one in the JSON file.
-- `resolution`: Type object. An object with the `dotsPerMeterX` and
+- `resolution`: Type `object`. An object with the `dotsPerMeterX` and
 `dotsPerMeterY` (integer) values ​​of the image.
-- `seeAlso`: Type string. More info about the object. Normally used to point
+- `seeAlso`: Type `string`. More info about the object. Normally used to point
 to bug reports. Not used by the test.
+- `skipSequential`: Type `boolean`. Skip the test on sequential access device.
+Some plugins may have limited functionality on sequential devices (e.g., 
+not reading metadata).
 - `unsupportedFormat`: Type `boolean`. When true, the test is skipped.
 
 Some examples:
@@ -169,11 +172,12 @@ See also [Add a test to CMakeLists.txt](#add-a-test-to-cmakeliststxt).
 The properties file must be located in `write/basic` and must have the name 
 of the file format (e.g. jxl.json). It is a JSON object composed of the 
 following values:
-- `format`: Type string. The format tested.
-- `metadata`: Type Array. An array of key/value objects (string type) 
+- `format`: Type `string`. The format tested.
+- `metadata`: Type `array`. An array of key/value objects (string type) 
 containing the image metadata as returned by `QImage::text`.
-- `resolution`: Type object. An object with the `dotsPerMeterX` and `
+- `resolution`: Type `object`. An object with the `dotsPerMeterX` and `
 dotsPerMeterY` (integer) values ​​of the image.
+- `subType`: type `string`. The image writer subtype to set when testing.
 
 [This is an example](write/basic/jxl.json) of property file.
 

autotests/read/tga/bottom_left.tga.json

@@ -0,0 +1,5 @@
+[
+    {
+        "fileName" : "orientation.png"
+    }
+]

autotests/read/tga/bottom_right.tga.json

@@ -0,0 +1,5 @@
+[
+    {
+        "fileName" : "orientation.png"
+    }
+]

autotests/read/tga/devarea.tga.json

@@ -0,0 +1,56 @@
+[
+    {
+        "fileName" : "extarea.png",
+        "skipSequential" : true,
+        "metadata" : [
+            {
+                "key" : "Author",
+                "value" : "KDE Project"
+            },
+            {
+                "key" : "Comment",
+                "value" : "TV broadcast test image."
+            },
+            {
+                "key" : "Altitude",
+                "value" : "34"
+            },
+            {
+                "key" : "Copyright",
+                "value" : "@2025 KDE Project"
+            },
+            {
+                "key" : "Latitude",
+                "value" : "44.6478"
+            },
+            {
+                "key" : "LensManufacturer",
+                "value" : "KDE Glasses"
+            },
+            {
+                "key" : "LensModel",
+                "value" : "A1234"
+            },
+            {
+                "key" : "Longitude",
+                "value" : "10.9254"
+            },
+            {
+                "key" : "Manufacturer",
+                "value" : "KFramework"
+            },
+            {
+                "key" : "Model",
+                "value" : "KImageFormats"
+            },
+            {
+                "key" : "Software",
+                "value" : "LIFE Pro 2.18.30 (Linux)"
+            }
+        ],
+        "resolution" : {
+            "dotsPerMeterX" : 11811,
+            "dotsPerMeterY" : 5906
+        }
+    }
+]

autotests/read/tga/extarea.tga.json

@@ -0,0 +1,32 @@
+[
+    {
+        "fileName" : "extarea.png",
+        "skipSequential" : true,
+        "metadata" : [
+            {
+                "key" : "Title",
+                "value" : "Test Card"
+            },
+            {
+                "key" : "Author",
+                "value" : "KDE Project"
+            },
+            {
+                "key" : "ModificationDate",
+                "value" : "2025-08-21T07:32:45"
+            },
+            {
+                "key" : "Comment",
+                "value" : "TV broadcast test image."
+            },
+            {
+                "key" : "Software",
+                "value" : "LIFE Pro 2.18.31 (Linux)"
+            }
+        ],
+        "resolution" : {
+            "dotsPerMeterX" : 3937,
+            "dotsPerMeterY" : 3937
+        }
+    }
+]

autotests/read/tga/top_left.tga.json

@@ -0,0 +1,5 @@
+[
+    {
+        "fileName" : "orientation.png"
+    }
+]

autotests/read/tga/top_right.tga.json

@@ -0,0 +1,5 @@
+[
+    {
+        "fileName" : "orientation.png"
+    }
+]

autotests/readtest.cpp

@@ -281,6 +281,12 @@ int main(int argc, char **argv)
                 continue;
             }
 
+            if (seq && timg.skipSequentialDeviceTest()) {
+                QTextStream(stdout) << "SKIP : " << fi.fileName() << ": marked to be skipped on a sequential device (don't worry, it's ok)\n";
+                ++skipped;
+                continue;
+            }
+
             TemplateImage::TestFlags flags = TemplateImage::None;
             QString comment;
             QFileInfo expFileInfo = timg.compareImage(flags, comment);

autotests/templateimage.cpp

@@ -76,6 +76,15 @@ bool TemplateImage::isLicense() const
     return !m_fi.suffix().compare(QStringLiteral("license"), Qt::CaseInsensitive);
 }
 
+bool TemplateImage::skipSequentialDeviceTest() const
+{
+    auto obj = searchObject(m_fi);
+    if (obj.isEmpty()) {
+        return false;
+    }
+    return obj.value("skipSequential").toBool();
+}
+
 QFileInfo TemplateImage::compareImage(TestFlags &flags, QString& comment) const
 {
     auto fi = jsonImage(flags, comment);

autotests/templateimage.h

@@ -54,6 +54,12 @@ public:
      */
     bool isLicense() const;
 
+    /*!
+     * \brief skipSequentialDeviceTest
+     * \return tre it the sequential test should be skipped.
+     */
+    bool skipSequentialDeviceTest() const;
+
     /*!
      * \brief compareImage
      * \param flags Flags for modifying test behavior (e.g. image format not supported by current Qt version).

autotests/write/basic/tga.json

@@ -0,0 +1,62 @@
+{
+    "format" : "tga",
+    "subType" : "TGAv2E",
+    "metadata" : [
+        {
+            "key" : "CreationDate",
+            "value" : "2025-01-14T13:53:32+01:00"
+        },
+        {
+            "key" : "Direction",
+            "value" : "123.7"
+        },
+        {
+            "key" : "Software" ,
+            "value" : "Adobe Photoshop 26.2 (Windows)"
+        },
+        {
+            "key" : "Altitude",
+            "value" : "34"
+        },
+        {
+            "key" : "Author",
+            "value" : "KDE Project"
+        },
+        {
+            "key" : "Copyright",
+            "value" : "@2025 KDE Project"
+        },
+        {
+            "key" : "Description",
+            "value" : "テレビ放送テスト映像。(TV broadcast test image.)"
+        },
+        {
+            "key" : "Latitude",
+            "value" : "44.6478"
+        },
+        {
+            "key" : "LensManufacturer",
+            "value" : "KDE Glasses"
+        },
+        {
+            "key" : "LensModel",
+            "value" : "A1234"
+        },
+        {
+            "key" : "Longitude",
+            "value" : "10.9254"
+        },
+        {
+            "key" : "Manufacturer",
+            "value" : "KFramework"
+        },
+        {
+            "key" : "Model",
+            "value" : "KImageFormats"
+        }
+    ],
+    "resolution" : {
+        "dotsPerMeterX" : 11811,
+        "dotsPerMeterY" : 11812
+    }
+}

autotests/writetest.cpp

@@ -70,6 +70,15 @@ void setOptionalInfo(QImage &image, const QString &suffix)
     }
 }
 
+QByteArray readSubType(const QString &suffix)
+{
+    auto obj = readOptionalInfo(suffix);
+    if (obj.isEmpty()) {
+        return {};
+    }
+    return obj.value("subType").toString().toLatin1();
+}
+
 bool checkOptionalInfo(QImage &image, const QString &suffix)
 {
     auto obj = readOptionalInfo(suffix);
@@ -157,6 +166,9 @@ int basicTest(const QString &suffix, bool lossless, bool ignoreDataCheck, bool s
         {
             QBuffer buffer(&writtenData);
             QImageWriter imgWriter(&buffer, format.constData());
+            auto subType = readSubType(suffix);
+            if (!subType.isEmpty())
+                imgWriter.setSubType(subType);
             if (lossless) {
                 imgWriter.setQuality(100);
             }

src/imageformats/CMakeLists.txt

@@ -137,7 +137,7 @@ kimageformats_add_plugin(kimg_sct SOURCES sct.cpp)
 
 ##################################
 
-kimageformats_add_plugin(kimg_tga SOURCES tga.cpp)
+kimageformats_add_plugin(kimg_tga SOURCES tga.cpp microexif.cpp scanlineconverter.cpp)
 
 ##################################
 

src/imageformats/tga_p.h

@@ -22,17 +22,20 @@ public:
     bool write(const QImage &image) override;
 
     bool supportsOption(QImageIOHandler::ImageOption option) const override;
+    void setOption(ImageOption option, const QVariant &value) override;
     QVariant option(QImageIOHandler::ImageOption option) const override;
 
     static bool canRead(QIODevice *device);
 
 private:
     bool writeIndexed(const QImage &image);
-
     bool writeGrayscale(const QImage &image);
-
+    bool writeRGB555(const QImage &image);
     bool writeRGBA(const QImage &image);
 
+    bool writeMetadata(const QImage &image);
+    bool readMetadata(QImage &image);
+
     const QScopedPointer<TGAHandlerPrivate> d;
 };