ImageData (and Images loaded from them) now support different data formats. Resolves issue #1048.

Currently exposed formats are rgba8 and rgba16 (normalized), and rgba16f and rgba32f (floating-point). Some systems, especially mobile ones, won't support every format when creating a love.graphics Image. Use love.graphics.getRawImageFormats to check for support.

love.image.newImageData now takes an optional format parameter as its third argument when creating an empty sized ImageData. It defaults to rgba8.

16-bit PNGs, .hdr images, and floating-point OpenEXR images can now be loaded via love.image.newImageData and love.graphics.newImage.

--HG--
branch : minor

src/modules/graphics/opengl/Graphics.cpp

@@ -1600,7 +1600,7 @@ love::image::ImageData *Graphics::newScreenshot(love::image::Image *image, bool
 	{
 		// Tell the new ImageData that it owns the screenshot data, so we don't
 		// need to delete it here.
-		img = image->newImageData(w, h, (void *) screenshot, true);
+		img = image->newImageData(w, h, image::ImageData::FORMAT_RGBA8, screenshot, true);
 	}
 	catch (love::Exception &)
 	{