Trade: restrict multi-level image conversion to same flags as well.

They are required to have the same format already, so flags make sense
as well -- what's the point of saving a multi-level cube map with one of
the levels being just a 2D array, anyway?

src/Magnum/Trade/AbstractImageConverter.cpp

@@ -537,6 +537,7 @@ template<UnsignedInt dimensions> bool checkImageValidity(const char* const messa
 
     const PixelFormat format = imageLevels[0].format();
     const UnsignedInt formatExtra = imageLevels[0].formatExtra();
+    const ImageFlags<dimensions> flags = imageLevels[0].flags();
     /* Going through *all* levels although the format assertion is never fired
        in the first iteration in order to properly check also the first one for
        zero size / nullptr. */
@@ -549,6 +550,8 @@ template<UnsignedInt dimensions> bool checkImageValidity(const char* const messa
             messagePrefix << "levels don't have the same format, expected" << format << "but got" << imageLevels[i].format() << "for image" << i, false);
         CORRADE_ASSERT(imageLevels[i].formatExtra() == formatExtra,
             messagePrefix << "levels don't have the same extra format field, expected" << formatExtra << "but got" << imageLevels[i].formatExtra() << "for image" << i, false);
+        CORRADE_ASSERT(imageLevels[i].flags() == flags,
+            messagePrefix << "levels don't have the same flags, expected" << flags << "but got" << imageLevels[i].flags() << "for image" << i, false);
     }
 
     return true;
@@ -559,6 +562,7 @@ template<UnsignedInt dimensions> bool checkImageValidity(const char* const messa
         messagePrefix << "at least one image has to be specified", false);
 
     const CompressedPixelFormat format = imageLevels[0].format();
+    const ImageFlags<dimensions> flags = imageLevels[0].flags();
     /* Going through *all* levels although the format assertion is never fired
        in the first iteration in order to properly check also the first one for
        zero size / nullptr. */
@@ -569,6 +573,8 @@ template<UnsignedInt dimensions> bool checkImageValidity(const char* const messa
             messagePrefix << "can't convert image" << i << "with a nullptr view", false);
         CORRADE_ASSERT(imageLevels[i].format() == format,
             messagePrefix << "levels don't have the same format, expected" << format << "but got" << imageLevels[i].format() << "for image" << i, false);
+        CORRADE_ASSERT(imageLevels[i].flags() == flags,
+            messagePrefix << "levels don't have the same flags, expected" << flags << "but got" << imageLevels[i].flags() << "for image" << i, false);
     }
 
     return true;

src/Magnum/Trade/AbstractImageConverter.h

@@ -612,10 +612,10 @@ checked by the implementation:
 -   All @ref doConvertToData() and @ref doConvertToFile() functions taking
     multiple (compressed) images are called only if the list has at least one
     image, each of the images has a non-zero size, the views are not
-    @cpp nullptr @ce and additionally all views have the same pixel format.
-    Since file formats have varying requirements on image level sizes and their
-    order and some don't impose any requirements at all, the plugin
-    implementation is expected to check the sizes on its own.
+    @cpp nullptr @ce and additionally all views have the same pixel format and
+    layout flags. Since file formats have varying requirements on image level
+    sizes and their order and some don't impose any requirements at all, the
+    plugin implementation is expected to check the sizes on its own.
 
 @m_class{m-block m-warning}
 
@@ -1082,11 +1082,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * Available only if @ref ImageConverterFeature::ConvertLevels1DToData
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
-         * non-zero size, and all of them sharing the same pixel format. Note
-         * that certain converters may impose additional size and order
-         * restrictions on the images, see documentation of a particular plugin
-         * for more information. On failure prints a message to
-         * @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
+         * non-zero size, and all of them sharing the same pixel format and
+         * layout flags. Note that certain converters may impose additional
+         * size and order restrictions on the images, see documentation of a
+         * particular plugin for more information. On failure prints a message
+         * to @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
          * @see @ref features(), @ref convertToData(Containers::ArrayView<const CompressedImageView1D>),
          *      @ref convert(), @ref convertToFile()
          */
@@ -1115,10 +1115,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @ref Containers::NullOpt.
          * @see @ref features(), @ref convertToData(Containers::ArrayView<const CompressedImageView2D>),
          *      @ref convert(), @ref convertToFile()
          */
@@ -1147,10 +1148,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @ref Containers::NullOpt.
          * @see @ref features(), @ref convertToData(Containers::ArrayView<const CompressedImageView3D>),
          *      @ref convert(), @ref convertToFile()
          */
@@ -1178,11 +1180,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * Available only if @ref ImageConverterFeature::ConvertCompressedLevels1DToData
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
-         * non-zero size, and all views sharing the same pixel format. Note
-         * that certain converters may impose additional size and order
-         * restrictions on the images, see documentation of a particular plugin
-         * for more information. On failure prints a message to
-         * @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
+         * non-zero size, and all views sharing the same pixel format and
+         * layout flags. Note that certain converters may impose additional
+         * size and order restrictions on the images, see documentation of a
+         * particular plugin for more information. On failure prints a message
+         * to @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
          * @see @ref features(), @ref convertToData(Containers::ArrayView<const ImageView1D>),
          *      @ref convert(), @ref convertToFile()
          */
@@ -1211,10 +1213,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @ref Containers::NullOpt.
          * @see @ref features(), @ref convertToData(Containers::ArrayView<const ImageView2D>),
          *      @ref convert(), @ref convertToFile()
          */
@@ -1243,10 +1246,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @ref Containers::NullOpt.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @ref Containers::NullOpt.
          * @see @ref features(), @ref convertToData(Containers::ArrayView<const ImageView3D>),
          *      @ref convert(), @ref convertToFile()
          */
@@ -1465,10 +1469,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @cpp false @ce.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @cpp false @ce.
          * @see @ref features(), @ref convertToFile(Containers::ArrayView<const CompressedImageView2D>, Containers::StringView),
          *      @ref convert(), @ref convertToData()
          */
@@ -1487,10 +1492,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @cpp false @ce.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @cpp false @ce.
          * @see @ref features(), @ref convertToFile(Containers::ArrayView<const CompressedImageView3D>, Containers::StringView),
          *      @ref convert(), @ref convertToData()
          */
@@ -1508,11 +1514,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * Available only if @ref ImageConverterFeature::ConvertCompressedLevels1DToFile
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
-         * non-zero size, and all views sharing the same pixel format. Note
-         * that certain converters may impose additional size and order
-         * restrictions on the images, see documentation of a particular plugin
-         * for more information. On failure prints a message to
-         * @relativeref{Magnum,Error} and returns @cpp false @ce.
+         * non-zero size, and all views sharing the same pixel format and
+         * layout flags. Note that certain converters may impose additional
+         * size and order restrictions on the images, see documentation of a
+         * particular plugin for more information. On failure prints a message
+         * to @relativeref{Magnum,Error} and returns @cpp false @ce.
          * @see @ref features(), @ref convertToFile(Containers::ArrayView<const ImageView1D>, Containers::StringView),
          *      @ref convert(), @ref convertToData()
          */
@@ -1531,10 +1537,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @cpp false @ce.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @cpp false @ce.
          * @see @ref features(), @ref convertToFile(Containers::ArrayView<const ImageView2D>, Containers::StringView),
          *      @ref convert(), @ref convertToData()
          */
@@ -1553,10 +1560,11 @@ class MAGNUM_TRADE_EXPORT AbstractImageConverter: public PluginManager::Abstract
          * is supported. The function expects at least one image to be passed,
          * with each view expected to not be @cpp nullptr @ce, to have a
          * non-zero size in all dimensions, and all views sharing the same
-         * pixel format. Note that certain converters may impose additional
-         * size and order restrictions on the images, see documentation of a
-         * particular plugin for more information. On failure prints a message
-         * to @relativeref{Magnum,Error} and returns @cpp false @ce.
+         * pixel format and layout flags. Note that certain converters may
+         * impose additional size and order restrictions on the images, see
+         * documentation of a particular plugin for more information. On
+         * failure prints a message to @relativeref{Magnum,Error} and returns
+         * @cpp false @ce.
          * @see @ref features(), @ref convertToFile(Containers::ArrayView<const ImageView3D>, Containers::StringView),
          *      @ref convert(), @ref convertToData()
          */

src/Magnum/Trade/Test/AbstractImageConverterTest.cpp

@@ -142,6 +142,7 @@ struct AbstractImageConverterTest: TestSuite::Tester {
     void convertLevels2DToDataNullptr();
     void convertLevels2DToDataInconsistentFormat();
     void convertLevels2DToDataInconsistentFormatExtra();
+    void convertLevels2DToDataInconsistentFlags();
     void convertLevels3DToDataInvalidImage();
     void convertLevels1DToDataNotImplemented();
     void convertLevels2DToDataNotImplemented();
@@ -165,6 +166,7 @@ struct AbstractImageConverterTest: TestSuite::Tester {
     void convertCompressedLevels2DToDataZeroSize();
     void convertCompressedLevels2DToDataNullptr();
     void convertCompressedLevels2DToDataInconsistentFormat();
+    void convertCompressedLevels2DToDataInconsistentFlags();
     void convertCompressedLevels3DToDataInvalidImage();
     void convertCompressedLevels1DToDataNotImplemented();
     void convertCompressedLevels2DToDataNotImplemented();
@@ -384,6 +386,7 @@ AbstractImageConverterTest::AbstractImageConverterTest() {
               &AbstractImageConverterTest::convertLevels2DToDataNullptr,
               &AbstractImageConverterTest::convertLevels2DToDataInconsistentFormat,
               &AbstractImageConverterTest::convertLevels2DToDataInconsistentFormatExtra,
+              &AbstractImageConverterTest::convertLevels2DToDataInconsistentFlags,
               &AbstractImageConverterTest::convertLevels3DToDataInvalidImage,
               &AbstractImageConverterTest::convertLevels1DToDataNotImplemented,
               &AbstractImageConverterTest::convertLevels2DToDataNotImplemented,
@@ -403,6 +406,7 @@ AbstractImageConverterTest::AbstractImageConverterTest() {
               &AbstractImageConverterTest::convertCompressedLevels2DToDataZeroSize,
               &AbstractImageConverterTest::convertCompressedLevels2DToDataNullptr,
               &AbstractImageConverterTest::convertCompressedLevels2DToDataInconsistentFormat,
+              &AbstractImageConverterTest::convertCompressedLevels2DToDataInconsistentFlags,
               &AbstractImageConverterTest::convertCompressedLevels3DToDataInvalidImage,
               &AbstractImageConverterTest::convertCompressedLevels1DToDataNotImplemented,
               &AbstractImageConverterTest::convertCompressedLevels2DToDataNotImplemented,
@@ -1986,6 +1990,26 @@ void AbstractImageConverterTest::convertLevels2DToDataInconsistentFormatExtra()
     CORRADE_COMPARE(out.str(), "Trade::AbstractImageConverter::convertToData(): levels don't have the same extra format field, expected 1037 but got 4467 for image 2\n");
 }
 
+void AbstractImageConverterTest::convertLevels2DToDataInconsistentFlags() {
+    #ifdef CORRADE_NO_ASSERT
+    CORRADE_SKIP("CORRADE_NO_ASSERT defined, can't test assertions");
+    #endif
+
+    struct: AbstractImageConverter {
+        ImageConverterFeatures doFeatures() const override { return ImageConverterFeature::ConvertLevels2DToData; }
+    } converter;
+
+    const char data[16]{};
+    std::ostringstream out;
+    Error redirectError{&out};
+    converter.convertToData({
+        ImageView2D{PixelFormat::RGBA8Unorm, {2, 2}, data, ImageFlag2D::Array},
+        ImageView2D{PixelFormat::RGBA8Unorm, {1, 1}, data, ImageFlag2D::Array},
+        ImageView2D{PixelFormat::RGBA8Unorm, {4, 1}, data}
+    });
+    CORRADE_COMPARE(out.str(), "Trade::AbstractImageConverter::convertToData(): levels don't have the same flags, expected ImageFlag2D::Array but got ImageFlags2D{} for image 2\n");
+}
+
 void AbstractImageConverterTest::convertLevels3DToDataInvalidImage() {
     #ifdef CORRADE_NO_ASSERT
     CORRADE_SKIP("CORRADE_NO_ASSERT defined, can't test assertions");
@@ -2308,6 +2332,26 @@ void AbstractImageConverterTest::convertCompressedLevels2DToDataInconsistentForm
     CORRADE_COMPARE(out.str(), "Trade::AbstractImageConverter::convertToData(): levels don't have the same format, expected CompressedPixelFormat::Bc1RGBAUnorm but got CompressedPixelFormat::Bc1RGBASrgb for image 2\n");
 }
 
+void AbstractImageConverterTest::convertCompressedLevels2DToDataInconsistentFlags() {
+    #ifdef CORRADE_NO_ASSERT
+    CORRADE_SKIP("CORRADE_NO_ASSERT defined, can't test assertions");
+    #endif
+
+    struct: AbstractImageConverter {
+        ImageConverterFeatures doFeatures() const override { return ImageConverterFeature::ConvertCompressedLevels2DToData; }
+    } converter;
+
+    const char data[16]{};
+    std::ostringstream out;
+    Error redirectError{&out};
+    converter.convertToData({
+        CompressedImageView2D{CompressedPixelFormat::Bc1RGBAUnorm, {8, 4}, data, ImageFlag2D::Array},
+        CompressedImageView2D{CompressedPixelFormat::Bc1RGBAUnorm, {4, 4}, data, ImageFlag2D::Array},
+        CompressedImageView2D{CompressedPixelFormat::Bc1RGBAUnorm, {4, 4}, data},
+    });
+    CORRADE_COMPARE(out.str(), "Trade::AbstractImageConverter::convertToData(): levels don't have the same flags, expected ImageFlag2D::Array but got ImageFlags2D{} for image 2\n");
+}
+
 void AbstractImageConverterTest::convertCompressedLevels3DToDataInvalidImage() {
     #ifdef CORRADE_NO_ASSERT
     CORRADE_SKIP("CORRADE_NO_ASSERT defined, can't test assertions");