Move ImageData scaling logic to Image #62

This commit contributes to moving the logic for scaling the ImageData
using GC from DPIUtil to Image for each platform and DPIUtil calls the
platform specific code from the method DPIUtil:autoScaleImageData.

contributes to
#62 and
#127

Author: amartya4256

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

@@ -1801,5 +1801,28 @@ public String toString () {
 	return "Image {" + handle + "}";
 }
 
+/**
+ * <b>IMPORTANT:</b> This method is not part of the public
+ * API for Image. It is marked public only so that it
+ * can be shared within the packages provided by SWT.
+ *
+ * Draws a scaled image using the GC by another image.
+ *
+ * @param gc the GC to draw on the resulting image
+ * @param original the image which is supposed to be scaled and drawn on the resulting image
+ * @param width the width of the original image
+ * @param height the height of the original image
+ * @param scaleFactor the factor with which the image is supposed to be scaled
+ *
+ * @noreference This method is not intended to be referenced by clients.
+ */
+public static void drawScaled(GC gc, Image original, int width, int height, float scaleFactor) {
+	gc.drawImage (original, 0, 0, DPIUtil.autoScaleDown (width), DPIUtil.autoScaleDown (height),
+			/* E.g. destWidth here is effectively DPIUtil.autoScaleDown (scaledWidth), but avoiding rounding errors.
+			 * Nevertheless, we still have some rounding errors due to the point-based API GC#drawImage(..).
+			 */
+			0, 0, Math.round (DPIUtil.autoScaleDown (width * scaleFactor)), Math.round (DPIUtil.autoScaleDown (height * scaleFactor)));
+}
+
 }
 

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

@@ -312,11 +312,7 @@ private static ImageData autoScaleImageData (Device device, final ImageData imag
 		Image resultImage = new Image (device, (ImageDataProvider) zoom -> resultData);
 		GC gc = new GC (resultImage);
 		gc.setAntialias (SWT.ON);
-		gc.drawImage (original, 0, 0, autoScaleDown (width), autoScaleDown (height),
-				/* E.g. destWidth here is effectively DPIUtil.autoScaleDown (scaledWidth), but avoiding rounding errors.
-				 * Nevertheless, we still have some rounding errors due to the point-based API GC#drawImage(..).
-				 */
-				0, 0, Math.round (autoScaleDown (width * scaleFactor)), Math.round (autoScaleDown (height * scaleFactor)));
+		Image.drawScaled(gc, original, width, height, scaleFactor);
 		gc.dispose ();
 		original.dispose ();
 		ImageData result = resultImage.getImageData (getDeviceZoom ());

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

@@ -1551,4 +1551,27 @@ public String toString () {
 	return "Image {" + surface + "}";
 }
 
+/**
+ * <b>IMPORTANT:</b> This method is not part of the public
+ * API for Image. It is marked public only so that it
+ * can be shared within the packages provided by SWT.
+ *
+ * Draws a scaled image using the GC by another image.
+ *
+ * @param gc the GC to draw on the resulting image
+ * @param original the image which is supposed to be scaled and drawn on the resulting image
+ * @param width the width of the original image
+ * @param height the height of the original image
+ * @param scaleFactor the factor with which the image is supposed to be scaled
+ *
+ * @noreference This method is not intended to be referenced by clients.
+ */
+public static void drawScaled(GC gc, Image original, int width, int height, float scaleFactor) {
+	gc.drawImage (original, 0, 0, DPIUtil.autoScaleDown (width), DPIUtil.autoScaleDown (height),
+			/* E.g. destWidth here is effectively DPIUtil.autoScaleDown (scaledWidth), but avoiding rounding errors.
+			 * Nevertheless, we still have some rounding errors due to the point-based API GC#drawImage(..).
+			 */
+			0, 0, Math.round (DPIUtil.autoScaleDown (width * scaleFactor)), Math.round (DPIUtil.autoScaleDown (height * scaleFactor)));
+}
+
 }

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

@@ -823,6 +823,26 @@ public static long win32_getHandle (Image image, int zoom) {
 	return image.getImageMetadata(zoom).handle;
 }
 
+/**
+ * <b>IMPORTANT:</b> This method is not part of the public
+ * API for Image. It is marked public only so that it
+ * can be shared within the packages provided by SWT.
+ *
+ * Draws a scaled image using the GC by another image.
+ *
+ * @param gc the GC to draw on the resulting image
+ * @param original the image which is supposed to be scaled and drawn on the resulting image
+ * @param width the width of the original image
+ * @param height the height of the original image
+ * @param scaleFactor the factor with which the image is supposed to be scaled
+ *
+ * @noreference This method is not intended to be referenced by clients.
+ */
+public static void drawScaled(GC gc, Image original, int width, int height, float scaleFactor) {
+	gc.drawImage (original, 0, 0, width, height,
+			0, 0, Math.round (width * scaleFactor), Math.round (height * scaleFactor), false);
+}
+
 long [] createGdipImage() {
 	return createGdipImage(this.getZoom());
 }
@@ -1254,7 +1274,7 @@ private ImageData getScaledImageData (int zoom) {
 	}
 	TreeSet<Integer> availableZooms = new TreeSet<>(zoomLevelToImageHandle.keySet());
 	int closestZoom = Optional.ofNullable(availableZooms.higher(zoom)).orElse(availableZooms.lower(zoom));
-	return scaleImageData(getImageMetadata(closestZoom).getImageData(), zoom, closestZoom);
+	return DPIUtil.scaleImageData (device, getImageMetadata(closestZoom).getImageData(), zoom, closestZoom);
 }
 
 
@@ -1844,40 +1864,6 @@ public void setBackground(Color color) {
 	zoomLevelToImageHandle.values().forEach(imageHandle -> imageHandle.setBackground(backgroundColor));
 }
 
-private ImageData scaleImageData(final ImageData imageData, int targetZoom, int currentZoom) {
-	if (imageData == null || targetZoom == currentZoom || (device != null && !device.isAutoScalable())) return imageData;
-	float scaleFactor = (float) targetZoom / (float) currentZoom;
-	int width = imageData.width;
-	int height = imageData.height;
-	int scaledWidth = Math.round (width * scaleFactor);
-	int scaledHeight = Math.round (height * scaleFactor);
-	boolean useSmoothScaling = DPIUtil.isSmoothScalingEnabled() && imageData.getTransparencyType() != SWT.TRANSPARENCY_MASK;
-	if (useSmoothScaling) {
-		return scaleToUsingSmoothScaling(scaledWidth, scaledHeight, imageData);
-	}
-	return imageData.scaledTo (scaledWidth, scaledHeight);
-}
-
-private ImageData scaleToUsingSmoothScaling(int width, int height, ImageData imageData) {
-	Image original = new Image (device, (ImageDataProvider) zoom -> imageData);
-	/* 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 resultImage = new Image (device, (ImageDataProvider) zoom -> resultData);
-	GC gc = new GC (resultImage);
-	gc.setAntialias (SWT.ON);
-	gc.drawImage (original, 0, 0, imageData.width, imageData.height,
-			/* E.g. destWidth here is effectively DPIUtil.autoScaleDown (scaledWidth), but avoiding rounding errors.
-			 * Nevertheless, we still have some rounding errors due to the point-based API GC#drawImage(..).
-			 */
-			0, 0, width, height, false);
-	gc.dispose ();
-	original.dispose ();
-	ImageData result = resultImage.getImageData (resultImage.getZoom());
-	resultImage.dispose ();
-	return result;
-}
-
 private int getZoom() {
 	return DPIUtil.getZoomForAutoscaleProperty(initialNativeZoom);
 }
@@ -2254,7 +2240,7 @@ final ImageHandle getImageMetadata(int zoom) {
 
 	private ImageHandle initializeHandleFromSource(int zoom) {
 		ElementAtZoom<ImageData> imageDataAtZoom = loadImageData(zoom);
-		ImageData imageData = scaleImageData(imageDataAtZoom.element(), zoom, imageDataAtZoom.zoom());
+		ImageData imageData = DPIUtil.scaleImageData (device,imageDataAtZoom.element(), zoom, imageDataAtZoom.zoom());
 		imageData = adaptImageDataIfDisabledOrGray(imageData);
 		return init(imageData, zoom);
 	}