Added *Image::dataSize().

Will be used to compute size of data array needed to store image of
given size.

src/AbstractImage.cpp

@@ -26,6 +26,7 @@
 
 #include <Utility/Assert.h>
 
+#include "Math/Vector.h"
 #include "ColorFormat.h"
 
 namespace Magnum {
@@ -135,4 +136,18 @@ std::size_t AbstractImage::pixelSize(ColorFormat format, ColorType type) {
     CORRADE_ASSERT_UNREACHABLE();
 }
 
+template<UnsignedInt dimensions> std::size_t AbstractImage::dataSize(Math::Vector<dimensions, Int> size) const {
+    /** @todo Code this properly when all @fn_gl{PixelStore} parameters are implemented */
+    /* Row size, rounded to multiple of 4 bytes */
+    const std::size_t rowSize = ((size[0]*pixelSize() + 3)/4)*4;
+
+    /** @todo Can't this be done somewhat nicer? */
+    size[0] = 1;
+    return rowSize*size.product();
+}
+
+template std::size_t AbstractImage::dataSize<1>(Math::Vector<1, Int>) const;
+template std::size_t AbstractImage::dataSize<2>(Math::Vector<2, Int>) const;
+template std::size_t AbstractImage::dataSize<3>(Math::Vector<3, Int>) const;
+
 }

src/AbstractImage.h

@@ -79,6 +79,8 @@ class MAGNUM_EXPORT AbstractImage {
 
         ~AbstractImage() = default;
 
+        template<UnsignedInt dimensions> std::size_t dataSize(Math::Vector<dimensions, Int> size) const;
+
     #ifdef DOXYGEN_GENERATING_OUTPUT
     private:
     #else

src/BufferImage.h

@@ -88,6 +88,11 @@ template<UnsignedInt dimensions> class MAGNUM_EXPORT BufferImage: public Abstrac
         /** @brief %Image size */
         typename DimensionTraits<Dimensions, Int>::VectorType size() const { return _size; }
 
+        /** @copydoc Image::dataSize() */
+        std::size_t dataSize(const typename DimensionTraits<Dimensions, Int>::VectorType& size) const {
+            return AbstractImage::dataSize<dimensions>(size);
+        }
+
         /** @brief %Image buffer */
         Buffer& buffer() { return _buffer; }
 

src/Image.h

@@ -96,6 +96,17 @@ template<UnsignedInt dimensions> class Image: public AbstractImage {
         /** @brief %Image size */
         typename DimensionTraits<Dimensions, Int>::VectorType size() const { return _size; }
 
+        /**
+         * @brief Size of data required to store image of given size
+         *
+         * Takes color format, type and row alignment of this image into
+         * account.
+         * @see @ref pixelSize()
+         */
+        std::size_t dataSize(const typename DimensionTraits<Dimensions, Int>::VectorType& size) const {
+            return AbstractImage::dataSize<dimensions>(size);
+        }
+
         /**
          * @brief Pointer to raw data
          *

src/ImageReference.h

@@ -76,6 +76,11 @@ template<UnsignedInt dimensions> class ImageReference: public AbstractImage {
         /** @brief %Image size */
         constexpr typename DimensionTraits<Dimensions, Int>::VectorType size() const { return _size; }
 
+        /** @copydoc Image::dataSize() */
+        std::size_t dataSize(const typename DimensionTraits<Dimensions, Int>::VectorType& size) const {
+            return AbstractImage::dataSize<dimensions>(size);
+        }
+
         /** @brief Pointer to raw data */
         constexpr const unsigned char* data() const { return _data; }
 

src/Test/AbstractImageTest.cpp

@@ -26,6 +26,7 @@
 #include <TestSuite/Tester.h>
 
 #include "AbstractImage.h"
+#include "Image.h"
 #include "ColorFormat.h"
 
 namespace Magnum { namespace Test {
@@ -35,6 +36,7 @@ class AbstractImageTest: public TestSuite::Tester {
         explicit AbstractImageTest();
 
         void pixelSize();
+        void dataSize();
 
         void debugFormat();
         void debugType();
@@ -42,6 +44,7 @@ class AbstractImageTest: public TestSuite::Tester {
 
 AbstractImageTest::AbstractImageTest() {
     addTests({&AbstractImageTest::pixelSize,
+              &AbstractImageTest::dataSize,
 
               &AbstractImageTest::debugFormat,
               &AbstractImageTest::debugType});
@@ -54,6 +57,17 @@ void AbstractImageTest::pixelSize() {
     CORRADE_COMPARE(AbstractImage::pixelSize(ColorFormat::DepthStencil, ColorType::UnsignedInt248), 4);
 }
 
+void AbstractImageTest::dataSize() {
+    /* Verify that row size is properly rounded */
+    CORRADE_COMPARE(Image2D(ColorFormat::RGBA, ColorType::UnsignedByte).dataSize({}), 0);
+    CORRADE_COMPARE(Image2D(ColorFormat::Red, ColorType::UnsignedByte).dataSize({4, 2}), 8);
+    CORRADE_COMPARE(Image2D(ColorFormat::Red, ColorType::UnsignedByte).dataSize({2, 4}), 16);
+    CORRADE_COMPARE(Image2D(ColorFormat::RGBA, ColorType::UnsignedByte).dataSize(Vector2i(1)), 4);
+
+    CORRADE_COMPARE(Image2D(ColorFormat::RGBA, ColorType::UnsignedShort).dataSize({16, 8}),
+                    4*2*16*8);
+}
+
 void AbstractImageTest::debugFormat() {
     std::ostringstream o;
     Debug(&o) << ColorFormat::RGBA;

src/Trade/ImageData.h

@@ -86,6 +86,11 @@ template<UnsignedInt dimensions> class ImageData: public AbstractImage {
         /** @brief %Image size */
         typename DimensionTraits<Dimensions, Int>::VectorType size() const { return _size; }
 
+        /** @copydoc Image::dataSize() */
+        std::size_t dataSize(const typename DimensionTraits<Dimensions, Int>::VectorType& size) const {
+            return AbstractImage::dataSize<dimensions>(size);
+        }
+
         /**
          * @brief Pointer to raw data
          *