Trade: reworked AbstractImageConverter plugin interface.

Implementation is moved into private virtual `do*()` functions and
public interface does additional sanity checks around them. Exporting to
file is by default done in base implementation, which takes exported
data and then saves them to the file.

Added unit test for file export, bumped plugin interface version to 0.2.

src/Trade/AbstractImageConverter.cpp

@@ -24,6 +24,7 @@
 
 #include "AbstractImageConverter.h"
 
+#include <fstream>
 #include <Containers/Array.h>
 #include <Utility/Assert.h>
 
@@ -33,25 +34,48 @@ AbstractImageConverter::AbstractImageConverter() = default;
 
 AbstractImageConverter::AbstractImageConverter(PluginManager::AbstractManager* manager, std::string plugin): AbstractPlugin(manager, std::move(plugin)) {}
 
-Image2D* AbstractImageConverter::convertToImage(const Image2D* const) const {
-    CORRADE_ASSERT(features() & Feature::ConvertToImage,
-        "Trade::AbstractImageConverter::convertToImage(): feature advertised but not implemented", nullptr);
+Image2D* AbstractImageConverter::exportToImage(const Image2D* const image) const {
+    CORRADE_ASSERT(features() & Feature::ConvertImage,
+        "Trade::AbstractImageConverter::exportToImage(): feature not supported", nullptr);
 
-    CORRADE_ASSERT(false, "Trade::AbstractImageConverter::convertToImage(): feature not implemented", nullptr);
+    return doExportToImage(image);
 }
 
-Containers::Array<unsigned char> AbstractImageConverter::convertToData(const Image2D* const) const {
-    CORRADE_ASSERT(features() & Feature::ConvertToData,
-        "Trade::AbstractImageConverter::convertToData(): feature advertised but not implemented", {});
+Image2D* AbstractImageConverter::doExportToImage(const Image2D*) const {
+    CORRADE_ASSERT(false, "Trade::AbstractImageConverter::exportToImage(): feature advertised but not implemented", nullptr);
+}
+
+Containers::Array<unsigned char> AbstractImageConverter::exportToData(const Image2D* const image) const {
+    CORRADE_ASSERT(features() & Feature::ConvertData,
+        "Trade::AbstractImageConverter::exportToData(): feature not supported", nullptr);
+
+    return doExportToData(image);
+}
 
-    CORRADE_ASSERT(false, "Trade::AbstractImageConverter::convertToData(): feature not implemented", {});
+Containers::Array<unsigned char> AbstractImageConverter::doExportToData(const Image2D*) const {
+    CORRADE_ASSERT(false, "Trade::AbstractImageConverter::exportToData(): feature advertised but not implemented", nullptr);
 }
 
-bool AbstractImageConverter::convertToFile(const Image2D* const, const std::string&) const {
-    CORRADE_ASSERT(features() & Feature::ConvertToFile,
-        "Trade::AbstractImageConverter::convertToFile(): feature advertised but not implemented", false);
+bool AbstractImageConverter::exportToFile(const Image2D* const image, const std::string& filename) const {
+    return doExportToFile(image, filename);
+}
+
+bool AbstractImageConverter::doExportToFile(const Image2D* const image, const std::string& filename) const {
+    CORRADE_ASSERT(features() & Feature::ConvertData, "Trade::AbstractImageConverter::exportToFile(): not implemented", nullptr);
+
+    auto data = doExportToData(image);
+    if(!data) return false;
+
+    /* Open file */
+    std::ofstream out(filename.data(), std::ios::binary);
+    if(!out.good()) {
+        Error() << "Trade::AbstractImageConverter::exportToFile(): cannot write to file" << filename;
+        return false;
+    }
 
-    CORRADE_ASSERT(false, "Trade::AbstractImageConverter::convertToFile(): feature not implemented", false);
+    /* Write data, close */
+    out.write(reinterpret_cast<const char*>(data.begin()), data.size());
+    return true;
 }
 
 }}

src/Trade/AbstractImageConverter.h

@@ -44,12 +44,19 @@ or compressing them.
 
 @section AbstractImageConverter-subclassing Subclassing
 
-Plugin implements function features() and one or more of convertToImage(),
-convertToData() or convertToFile() functions based on what features are
+Plugin implements function doFeatures() and one or more of doExportToImage(),
+doExportToData() or doExportToFile() functions based on what features are
 supported.
+
+You don't need to do most of the redundant sanity checks, these things are
+checked by the implementation:
+
+-   Functions doExportToImage() or doExportToData() are called only if
+    @ref Feature "Feature::ConvertImage" or @ref Feature "Feature::ConvertData"
+    is supported.
 */
 class MAGNUM_EXPORT AbstractImageConverter: public PluginManager::AbstractPlugin {
-    CORRADE_PLUGIN_INTERFACE("cz.mosra.magnum.Trade.AbstractImageConverter/0.1")
+    CORRADE_PLUGIN_INTERFACE("cz.mosra.magnum.Trade.AbstractImageConverter/0.2")
 
     public:
         /**
@@ -58,14 +65,11 @@ class MAGNUM_EXPORT AbstractImageConverter: public PluginManager::AbstractPlugin
          * @see Features, features()
          */
         enum class Feature: UnsignedByte {
-            /** Converting to image with different format with convertToImage() */
-            ConvertToImage = 1 << 0,
-
-            /** Converting to data with convertToData() */
-            ConvertToData = 1 << 1,
+            /** Conversion to image with different format with exportToImage() */
+            ConvertImage = 1 << 0,
 
-            /** Converting to file with convertToFile() */
-            ConvertToFile = 1 << 2
+            /** Exporting to raw data with exportToData() */
+            ConvertData = 1 << 1
         };
 
         /**
@@ -82,34 +86,56 @@ class MAGNUM_EXPORT AbstractImageConverter: public PluginManager::AbstractPlugin
         explicit AbstractImageConverter(PluginManager::AbstractManager* manager, std::string plugin);
 
         /** @brief Features supported by this converter */
-        virtual Features features() const = 0;
+        Features features() const { return doFeatures(); }
 
         /**
          * @brief Convert image to different format
          *
-         * Available only if @ref Feature "Feature::ConvertToImage" is supported.
+         * Available only if @ref Feature "Feature::ConvertImage" is supported.
          * Returns converted image on success, `nullptr` otherwise.
-         * @see features(), convertToData(), convertToFile()
+         * @see features(), exportToData(), exportToFile()
          */
-        virtual Image2D* convertToImage(const Image2D* image) const;
+        Image2D* exportToImage(const Image2D* image) const;
 
         /**
-         * @brief Convert image to raw data
+         * @brief Export image to raw data
          *
-         * Available only if @ref Feature "Feature::ConvertToData" is supported.
-         * Returns data pointer and size on success, `nullptr` otherwise.
-         * @see features(), convertToImage(), convertToFile()
+         * Available only if @ref Feature "Feature::ConvertData" is supported.
+         * Returns data on success, zero-sized array otherwise.
+         * @see features(), exportToImage(), exportToFile()
          */
-        virtual Containers::Array<unsigned char> convertToData(const Image2D* image) const;
+        Containers::Array<unsigned char> exportToData(const Image2D* image) const;
 
         /**
-         * @brief Convert image and save it to file
+         * @brief Export image to file
          *
-         * Available only if @ref Feature "Feature::ConvertToFile" is supported.
          * Returns `true` on success, `false` otherwise.
-         * @see features(), convertToImage(), convertToData()
+         * @see features(), exportToImage(), exportToData()
+         */
+        bool exportToFile(const Image2D* image, const std::string& filename) const;
+
+    #ifndef DOXYGEN_GENERATING_OUTPUT
+    private:
+    #else
+    protected:
+    #endif
+        /** @brief Implementation of features() */
+        virtual Features doFeatures() const = 0;
+
+        /** @brief Implementation of exportToImage() */
+        virtual Image2D* doExportToImage(const Image2D* image) const;
+
+        /** @brief Implementation of exportToData() */
+        virtual Containers::Array<unsigned char> doExportToData(const Image2D* image) const;
+
+        /**
+         * @brief Implementation of exportToFile()
+         *
+         * If @ref Feature "Feature::ConvertData" is supported, default
+         * implementation calls doExportToData() and saves the result to given
+         * file.
          */
-        virtual bool convertToFile(const Image2D* image, const std::string& filename) const;
+        virtual bool doExportToFile(const Image2D* image, const std::string& filename) const;
 };
 
 CORRADE_ENUMSET_OPERATORS(AbstractImageConverter::Features)

src/Trade/Test/AbstractImageConverterTest.cpp

@@ -0,0 +1,75 @@
+/*
+    This file is part of Magnum.
+
+    Copyright © 2010, 2011, 2012, 2013 Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+#include <Containers/Array.h>
+#include <TestSuite/Tester.h>
+#include <TestSuite/Compare/FileToString.h>
+#include <Utility/Directory.h>
+
+#include "Image.h"
+#include "ImageFormat.h"
+#include "Trade/AbstractImageConverter.h"
+
+#include "testConfigure.h"
+
+namespace Magnum { namespace Trade { namespace Test {
+
+class AbstractImageConverterTest: public TestSuite::Tester {
+    public:
+        explicit AbstractImageConverterTest();
+
+        void exportToFile();
+};
+
+AbstractImageConverterTest::AbstractImageConverterTest() {
+    addTests({&AbstractImageConverterTest::exportToFile});
+}
+
+void AbstractImageConverterTest::exportToFile() {
+    class DataExporter: public Trade::AbstractImageConverter {
+        private:
+            Features doFeatures() const override { return Feature::ConvertData; }
+
+            Containers::Array<unsigned char> doExportToData(const Image2D* image) const override {
+                Containers::Array<unsigned char> out(2);
+                out[0] = image->size().x();
+                out[1] = image->size().y();
+                return out;
+            };
+    };
+
+    /* Remove previous file */
+    Utility::Directory::rm(Utility::Directory::join(TRADE_TEST_OUTPUT_DIR, "image.out"));
+
+    /* doExportToFile() should call doExportToData() */
+    DataExporter exporter;
+    Image2D image({0xfe, 0xed}, ImageFormat::RGBA, ImageType::UnsignedByte, nullptr);
+    CORRADE_VERIFY(exporter.exportToFile(&image, Utility::Directory::join(TRADE_TEST_OUTPUT_DIR, "image.out")));
+    CORRADE_COMPARE_AS(Utility::Directory::join(TRADE_TEST_OUTPUT_DIR, "image.out"),
+        "\xFE\xED", TestSuite::Compare::FileToString);
+}
+
+}}}
+
+CORRADE_TEST_MAIN(Magnum::Trade::Test::AbstractImageConverterTest)

src/Trade/Test/CMakeLists.txt

@@ -27,6 +27,7 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/testConfigure.h.cmake
 
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 
+corrade_add_test(TradeAbstractImageConverterTest AbstractImageConverterTest.cpp LIBRARIES Magnum)
 corrade_add_test(TradeAbstractImporterTest AbstractImporterTest.cpp LIBRARIES Magnum)
 corrade_add_test(TradeObjectData2DTest ObjectData2DTest.cpp LIBRARIES Magnum)
 corrade_add_test(TradeObjectData3DTest ObjectData3DTest.cpp LIBRARIES Magnum)

src/Trade/Test/testConfigure.h.cmake

@@ -23,3 +23,4 @@
 */
 
 #define TRADE_TEST_DIR "${CMAKE_CURRENT_SOURCE_DIR}"
+#define TRADE_TEST_OUTPUT_DIR "${CMAKE_CURRENT_BINARY_DIR}"