Don't blow up in ImageView::pixels() if the image has empty data.

src/Magnum/ImageView.cpp

@@ -62,6 +62,7 @@ template<UnsignedInt dimensions, class T> void ImageView<dimensions, T>::setData
 }
 
 template<UnsignedInt dimensions, class T> auto ImageView<dimensions, T>::pixels() const -> Containers::StridedArrayView<dimensions + 1, Type> {
+    if(!_data && !_data.size()) return {};
     return Implementation::imagePixelView<dimensions, Type>(*this);
 }
 

src/Magnum/ImageView.h

@@ -430,7 +430,9 @@ template<UnsignedInt dimensions, class T> class ImageView {
          * @brief View on pixel data
          *
          * Provides direct and easy-to-use access to image pixels. See
-         * @ref Image-pixel-views for more information.
+         * @ref Image-pixel-views for more information. If the view is empty
+         * (with @ref data() being @cpp nullptr @ce), returns @cpp nullptr @ce
+         * as well.
          */
         Containers::StridedArrayView<dimensions + 1, Type> pixels() const;
 
@@ -440,9 +442,12 @@ template<UnsignedInt dimensions, class T> class ImageView {
          * Compared to non-templated @ref pixels() in addition casts the pixel
          * data to a specified type. The user is responsible for choosing
          * correct type for given @ref format() --- checking it on the library
-         * side is not possible for the general case.
+         * side is not possible for the general case. If the view is empty
+         * (with @ref data() being @cpp nullptr @ce), returns @cpp nullptr @ce
+         * as well.
          */
         template<class U> Containers::StridedArrayView<dimensions, typename std::conditional<std::is_const<Type>::value, typename std::add_const<U>::type, U>::type> pixels() const {
+            if(!_data && !_data.size()) return {};
             /* Deliberately not adding a StridedArrayView include, it should
                work without since this is a templated function */
             return Containers::arrayCast<dimensions, typename std::conditional<std::is_const<Type>::value, typename std::add_const<U>::type, U>::type>(pixels());

src/Magnum/Test/ImageViewTest.cpp

@@ -65,6 +65,7 @@ struct ImageViewTest: TestSuite::Tester {
     template<class T> void pixels1D();
     template<class T> void pixels2D();
     template<class T> void pixels3D();
+    void pixelsNullptr();
 };
 
 template<class> struct MutabilityTraits;
@@ -116,7 +117,8 @@ ImageViewTest::ImageViewTest() {
               &ImageViewTest::pixels2D<const char>,
               &ImageViewTest::pixels2D<char>,
               &ImageViewTest::pixels3D<const char>,
-              &ImageViewTest::pixels3D<char>});
+              &ImageViewTest::pixels3D<char>,
+              &ImageViewTest::pixelsNullptr});
 }
 
 namespace GL {
@@ -667,6 +669,21 @@ template<class T> void ImageViewTest::pixels3D() {
     CORRADE_COMPARE(pixels.data(), image.data() + 140 + 2*20 + 3*3);
 }
 
+void ImageViewTest::pixelsNullptr() {
+    ImageView3D image{PixelFormat::RGB8Unorm, {2, 4, 3}};
+
+    CORRADE_COMPARE(image.data(), nullptr);
+    CORRADE_COMPARE(image.data().size(), 0);
+
+    CORRADE_COMPARE(image.pixels().data(), nullptr);
+    CORRADE_COMPARE(image.pixels().size(),
+        Containers::StridedArrayView4D<const char>::Size{});
+
+    CORRADE_COMPARE(image.pixels<Color3ub>().data(), nullptr);
+    CORRADE_COMPARE(image.pixels<Color3ub>().size(),
+        Containers::StridedArrayView3D<Color3ub>::Size{});
+}
+
 }}}
 
 CORRADE_TEST_MAIN(Magnum::Test::ImageViewTest)