[win32] No handle creation on Image::getBounds

This commit adapts the bounds calculation in Image to not create any handle, but use and scale the bounds of an existing handle if no handle for the desired zoom is available

Fixes eclipse-platform#1639

Author: akoch-yatta

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

@@ -127,7 +127,7 @@ public final class Image extends Resource implements Drawable {
 	 */
 	static final int DEFAULT_SCANLINE_PAD = 4;
 
-	private HashMap<Integer, ImageHandle> zoomLevelToImageHandle = new HashMap<>();
+	private Map<Integer, ImageHandle> zoomLevelToImageHandle = new HashMap<>();
 
 /**
  * Prevents uninitialized instances from being created outside the package.
@@ -1303,8 +1303,14 @@ public Rectangle getBounds() {
 
 Rectangle getBounds(int zoom) {
 	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
-	ImageHandle imageMetadata = getImageMetadata(zoom);
-	return new Rectangle(0, 0, imageMetadata.width, imageMetadata.height);
+	ImageHandle imageMetadata;
+	if (zoomLevelToImageHandle.containsKey(zoom)) {
+		imageMetadata = zoomLevelToImageHandle.get(zoom);
+	} else {
+		imageMetadata = zoomLevelToImageHandle.values().iterator().next();
+	}
+	Rectangle rectangle = new Rectangle(0, 0, imageMetadata.width, imageMetadata.height);
+	return DPIUtil.scaleBounds(rectangle, zoom, imageMetadata.zoom);
 }
 
 /**
@@ -2084,18 +2090,19 @@ public void close() {
 
 private class ImageHandle {
 	final long handle;
+	final int zoom;
 	int height;
 	int width;
 
 	public ImageHandle(long handle, int zoom) {
 		Rectangle bounds = getBoundsInPixelsFromNative(handle);
 		this.handle = handle;
+		this.zoom = zoom;
 		this.height = bounds.height;
 		this.width = bounds.width;
 		setImageMetadataForHandle(this, zoom);
 	}
 
-
 	private Rectangle getBoundsInPixelsFromNative(long handle) {
 		switch (type) {
 		case SWT.BITMAP: