Use ImageGcDrawer for smooth scaling of ImageData

This commit adapts the smooth scaling implementation to use
ImageGcDrawer.

Author: akoch-yatta

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/graphics/Image.java

@@ -906,6 +906,7 @@ private ImageData drawWithImageGcDrawer(ImageGcDrawer imageGcDrawer, int width,
 	int gcStyle = imageGcDrawer.getGcStyle();
 	Image image;
 	if ((gcStyle & SWT.TRANSPARENT) != 0) {
+		/* Create a 24 bit image data with alpha channel */
 		final ImageData resultData = new ImageData (width, height, 24, new PaletteData (0xFF, 0xFF00, 0xFF0000));
 		resultData.alphaData = new byte [width * height];
 		image = new Image(device, resultData);

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/internal/DPIUtil.java

@@ -306,16 +306,21 @@ private static ImageData autoScaleImageData (Device device, final ImageData imag
 	boolean useSmoothScaling = isSmoothScalingEnabled() && imageData.getTransparencyType() != SWT.TRANSPARENCY_MASK;
 	if (useSmoothScaling) {
 		Image original = new Image (device, (ImageDataProvider) zoom -> imageData);
-		/* Create a 24 bit image data with alpha channel */
-		final ImageData resultData = new ImageData (scaledWidth, scaledHeight, 24, new PaletteData (0xFF, 0xFF00, 0xFF0000));
-		resultData.alphaData = new byte [scaledWidth * scaledHeight];
-		Image resultImage = new Image (device, (ImageDataProvider) zoom -> resultData);
-		GC gc = new GC (resultImage);
-		gc.setAntialias (SWT.ON);
-		Image.drawScaled(gc, original, width, height, scaleFactor);
-		gc.dispose ();
+		ImageGcDrawer drawer =  new ImageGcDrawer() {
+			@Override
+			public void drawOn(GC gc, int imageWidth, int imageHeight) {
+				gc.setAntialias (SWT.ON);
+				Image.drawScaled(gc, original, width, height, scaleFactor);
+			};
+
+			@Override
+			public int getGcStyle() {
+				return SWT.TRANSPARENT;
+			}
+		};
+		Image resultImage = new Image (device, drawer, scaledWidth, scaledHeight);
+		ImageData result = resultImage.getImageData (100);
 		original.dispose ();
-		ImageData result = resultImage.getImageData (getDeviceZoom ());
 		resultImage.dispose ();
 		return result;
 	} else {

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Image.java

@@ -1168,6 +1168,7 @@ private ImageData drawWithImageGcDrawer(int width, int height, int zoom) {
 	int gcStyle = imageGcDrawer.getGcStyle();
 	Image image;
 	if ((gcStyle & SWT.TRANSPARENT) != 0) {
+		/* Create a 24 bit image data with alpha channel */
 		final ImageData resultData = new ImageData(width, height, 24, new PaletteData (0xFF, 0xFF00, 0xFF0000));
 		resultData.alphaData = new byte [width * height];
 		image = new Image(device, resultData, zoom);
@@ -1288,7 +1289,7 @@ void init(ImageData image) {
 	init(image, DPIUtil.getDeviceZoom());
 }
 
-void init(ImageData image, int zoom) {
+private void init(ImageData image, int zoom) {
 	if (image == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 
 	PaletteData palette = image.palette;

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Image.java

@@ -1972,7 +1972,7 @@ private class PlainImageDataProviderWrapper extends ImageFromImageDataProviderWr
 		this(imageData, 100);
 	}
 
-	PlainImageDataProviderWrapper(ImageData imageData, int zoom) {
+	private PlainImageDataProviderWrapper(ImageData imageData, int zoom) {
 		this.imageDataAtBaseZoom = (ImageData) imageData.clone();
 		this.baseZoom = zoom;
 		initImage();
@@ -2499,6 +2499,7 @@ protected ImageHandle newImageHandle(int zoom) {
 		if ((gcStyle & SWT.TRANSPARENT) != 0) {
 			int scaledHeight = DPIUtil.scaleUp(height, zoom);
 			int scaledWidth = DPIUtil.scaleUp(width, zoom);
+			/* Create a 24 bit image data with alpha channel */
 			final ImageData resultData = new ImageData (scaledWidth, scaledHeight, 24, new PaletteData (0xFF, 0xFF00, 0xFF0000));
 			resultData.alphaData = new byte [scaledWidth * scaledHeight];
 			image = new Image(device, resultData, zoom);