Replaced the Image::getTag() method with a more versatile getProperties() method. Used this to set a flag called "originalImageHadAlpha" when loading images, which is set to indicate whether the original file had an alpha channel.

juce_amalgamated.cpp

@@ -95575,15 +95575,9 @@ const Image Image::convertedToFormat (PixelFormat newFormat) const
 	return newImage;
 }
 
-const var Image::getTag() const
+NamedValueSet* Image::getProperties() const
 {
-	return image == 0 ? var::null : image->userTag;
-}
-
-void Image::setTag (const var& newTag)
-{
-	if (image != 0)
-		image->userTag = newTag;
+	return image == 0 ? 0 : &(image->userData);
 }
 
 Image::BitmapData::BitmapData (Image& image, const int x, const int y, const int w, const int h, const bool /*makeWritable*/)
@@ -96480,6 +96474,8 @@ public:
 			image = Image ((transparent >= 0) ? Image::ARGB : Image::RGB,
 						   imageWidth, imageHeight, (transparent >= 0));
 
+			image.getProperties()->set ("originalImageHadAlpha", image.hasAlphaChannel());
+
 			readImage ((buf[8] & 0x40) != 0, transparent);
 
 			break;
@@ -211967,6 +211963,7 @@ const Image JPEGImageFormat::decodeImage (InputStream& in)
 			if (jpeg_start_decompress (&jpegDecompStruct))
 			{
 				image = Image (Image::RGB, width, height, false);
+				image.getProperties()->set ("originalImageHadAlpha", false);
 				const bool hasAlphaChan = image.hasAlphaChannel(); // (the native image creator may not give back what we expect)
 
 				const Image::BitmapData destData (image, true);
@@ -237674,6 +237671,7 @@ const Image PNGImageFormat::decodeImage (InputStream& in)
 		image = Image (hasAlphaChan ? Image::ARGB : Image::RGB,
 					   (int) width, (int) height, hasAlphaChan);
 
+		image.getProperties()->set ("originalImageHadAlpha", image.hasAlphaChannel());
 		hasAlphaChan = image.hasAlphaChannel(); // (the native image creator may not give back what we expect)
 
 		const Image::BitmapData destData (image, true);
@@ -267560,8 +267558,12 @@ const Image juce_loadWithCoreImage (InputStream& input)
 
 		if (loadedImage != 0)
 		{
-			const bool hasAlphaChan = CGImageGetAlphaInfo (loadedImage) != kCGImageAlphaNone;
-			Image image (hasAlphaChan ? Image::ARGB : Image::RGB,
+			CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo (loadedImage);
+			const bool hasAlphaChan = (alphaInfo != kCGImageAlphaNone
+										 && alphaInfo != kCGImageAlphaNoneSkipLast
+										 && alphaInfo != kCGImageAlphaNoneSkipFirst);
+
+			Image image (Image::ARGB, // (CoreImage doesn't work with 24-bit images)
 						 (int) CGImageGetWidth (loadedImage), (int) CGImageGetHeight (loadedImage),
 						 hasAlphaChan, Image::NativeImage);
 
@@ -267575,6 +267577,9 @@ const Image juce_loadWithCoreImage (InputStream& input)
 			CFRelease (loadedImage);
 #endif
 
+			// Because it's impossible to create a truly 24-bit CG image, this flag allows a user
+			// to find out whether the file they just loaded the image from had an alpha channel or not.
+			image.getProperties()->set ("originalImageHadAlpha", hasAlphaChan);
 			return image;
 		}
 	}
@@ -272254,8 +272259,12 @@ const Image juce_loadWithCoreImage (InputStream& input)
 
 		if (loadedImage != 0)
 		{
-			const bool hasAlphaChan = CGImageGetAlphaInfo (loadedImage) != kCGImageAlphaNone;
-			Image image (hasAlphaChan ? Image::ARGB : Image::RGB,
+			CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo (loadedImage);
+			const bool hasAlphaChan = (alphaInfo != kCGImageAlphaNone
+										 && alphaInfo != kCGImageAlphaNoneSkipLast
+										 && alphaInfo != kCGImageAlphaNoneSkipFirst);
+
+			Image image (Image::ARGB, // (CoreImage doesn't work with 24-bit images)
 						 (int) CGImageGetWidth (loadedImage), (int) CGImageGetHeight (loadedImage),
 						 hasAlphaChan, Image::NativeImage);
 
@@ -272269,6 +272278,9 @@ const Image juce_loadWithCoreImage (InputStream& input)
 			CFRelease (loadedImage);
 #endif
 
+			// Because it's impossible to create a truly 24-bit CG image, this flag allows a user
+			// to find out whether the file they just loaded the image from had an alpha channel or not.
+			image.getProperties()->set ("originalImageHadAlpha", hasAlphaChan);
 			return image;
 		}
 	}

juce_amalgamated.h

@@ -64,7 +64,7 @@
 */
 #define JUCE_MAJOR_VERSION	  1
 #define JUCE_MINOR_VERSION	  52
-#define JUCE_BUILDNUMBER	79
+#define JUCE_BUILDNUMBER	80
 
 /** Current Juce version number.
 
@@ -25352,21 +25352,12 @@ public:
 	void createSolidAreaMask (RectangleList& result,
 							  float alphaThreshold = 0.5f) const;
 
-	/** Returns a user-specified data item that was set with setTag().
-		setTag() and getTag() allow you to attach an arbitrary identifier value to an
-		image. The value is shared between all Image object that are referring to the
-		same underlying image data object.
-	*/
-	const var getTag() const;
-
-	/** Attaches a user-specified data item to this image, which can be retrieved using getTag().
-		setTag() and getTag() allow you to attach an arbitrary identifier value to an
-		image. The value is shared between all Image object that are referring to the
-		same underlying image data object.
+	/** Returns a NamedValueSet that is attached to the image and which can be used for
+		associating custom values with it.
 
-		Note that if this Image is null, this method will fail to store the data.
+		If this is a null image, this will return a null pointer.
 	*/
-	void setTag (const var& newTag);
+	NamedValueSet* getProperties() const;
 
 	/** Creates a context suitable for drawing onto this image.
 		Don't call this method directly! It's used internally by the Graphics class.
@@ -25411,7 +25402,7 @@ public:
 		const int width, height;
 		int pixelStride, lineStride;
 		uint8* imageData;
-		var userTag;
+		NamedValueSet userData;
 
 		SharedImage (const SharedImage&);
 		SharedImage& operator= (const SharedImage&);

src/core/juce_StandardHeader.h

@@ -33,7 +33,7 @@
 */
 #define JUCE_MAJOR_VERSION      1
 #define JUCE_MINOR_VERSION      52
-#define JUCE_BUILDNUMBER        79
+#define JUCE_BUILDNUMBER        80
 
 /** Current Juce version number.
 

src/gui/graphics/imaging/image_file_formats/juce_GIFLoader.cpp

@@ -104,6 +104,8 @@ public:
             image = Image ((transparent >= 0) ? Image::ARGB : Image::RGB,
                            imageWidth, imageHeight, (transparent >= 0));
 
+            image.getProperties()->set ("originalImageHadAlpha", image.hasAlphaChannel());
+
             readImage ((buf[8] & 0x40) != 0, transparent);
 
             break;

src/gui/graphics/imaging/image_file_formats/juce_JPEGLoader.cpp

@@ -304,6 +304,7 @@ const Image JPEGImageFormat::decodeImage (InputStream& in)
             if (jpeg_start_decompress (&jpegDecompStruct))
             {
                 image = Image (Image::RGB, width, height, false);
+                image.getProperties()->set ("originalImageHadAlpha", false);
                 const bool hasAlphaChan = image.hasAlphaChannel(); // (the native image creator may not give back what we expect)
 
                 const Image::BitmapData destData (image, true);

src/gui/graphics/imaging/image_file_formats/juce_PNGLoader.cpp

@@ -228,6 +228,7 @@ const Image PNGImageFormat::decodeImage (InputStream& in)
         image = Image (hasAlphaChan ? Image::ARGB : Image::RGB,
                        (int) width, (int) height, hasAlphaChan);
 
+        image.getProperties()->set ("originalImageHadAlpha", image.hasAlphaChannel());
         hasAlphaChan = image.hasAlphaChannel(); // (the native image creator may not give back what we expect)
 
         const Image::BitmapData destData (image, true);

src/gui/graphics/imaging/juce_Image.cpp

@@ -252,15 +252,9 @@ const Image Image::convertedToFormat (PixelFormat newFormat) const
     return newImage;
 }
 
-const var Image::getTag() const
+NamedValueSet* Image::getProperties() const
 {
-    return image == 0 ? var::null : image->userTag;
-}
-
-void Image::setTag (const var& newTag)
-{
-    if (image != 0)
-        image->userTag = newTag;
+    return image == 0 ? 0 : &(image->userData);
 }
 
 //==============================================================================

src/gui/graphics/imaging/juce_Image.h

@@ -29,7 +29,7 @@
 #include "../colour/juce_Colour.h"
 #include "../contexts/juce_Graphics.h"
 #include "../../../containers/juce_Variant.h"
-
+#include "../../../containers/juce_NamedValueSet.h"
 
 //==============================================================================
 /**
@@ -354,21 +354,12 @@ public:
                               float alphaThreshold = 0.5f) const;
 
     //==============================================================================
-    /** Returns a user-specified data item that was set with setTag().
-        setTag() and getTag() allow you to attach an arbitrary identifier value to an
-        image. The value is shared between all Image object that are referring to the
-        same underlying image data object.
-    */
-    const var getTag() const;
-
-    /** Attaches a user-specified data item to this image, which can be retrieved using getTag().
-        setTag() and getTag() allow you to attach an arbitrary identifier value to an
-        image. The value is shared between all Image object that are referring to the
-        same underlying image data object.
+    /** Returns a NamedValueSet that is attached to the image and which can be used for
+        associating custom values with it.
 
-        Note that if this Image is null, this method will fail to store the data.
+        If this is a null image, this will return a null pointer.
     */
-    void setTag (const var& newTag);
+    NamedValueSet* getProperties() const;
 
     //==============================================================================
     /** Creates a context suitable for drawing onto this image.
@@ -415,7 +406,7 @@ public:
         const int width, height;
         int pixelStride, lineStride;
         uint8* imageData;
-        var userTag;
+        NamedValueSet userData;
 
         SharedImage (const SharedImage&);
         SharedImage& operator= (const SharedImage&);

src/native/mac/juce_mac_CoreGraphicsContext.mm

@@ -800,8 +800,12 @@ const Image juce_loadWithCoreImage (InputStream& input)
 
         if (loadedImage != 0)
         {
-            const bool hasAlphaChan = CGImageGetAlphaInfo (loadedImage) != kCGImageAlphaNone;
-            Image image (hasAlphaChan ? Image::ARGB : Image::RGB,
+            CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo (loadedImage);
+            const bool hasAlphaChan = (alphaInfo != kCGImageAlphaNone
+                                         && alphaInfo != kCGImageAlphaNoneSkipLast
+                                         && alphaInfo != kCGImageAlphaNoneSkipFirst);
+
+            Image image (Image::ARGB, // (CoreImage doesn't work with 24-bit images)
                          (int) CGImageGetWidth (loadedImage), (int) CGImageGetHeight (loadedImage),
                          hasAlphaChan, Image::NativeImage);
 
@@ -815,6 +819,9 @@ const Image juce_loadWithCoreImage (InputStream& input)
             CFRelease (loadedImage);
 #endif
 
+            // Because it's impossible to create a truly 24-bit CG image, this flag allows a user
+            // to find out whether the file they just loaded the image from had an alpha channel or not.
+            image.getProperties()->set ("originalImageHadAlpha", hasAlphaChan);
             return image;
         }
     }