My application needs to resize ImageData. Unfortunately, I haven't gotten the results I want with GC (with antialias on and interpolation on high), or ImageData.scaledTo(). The resulting image is of too low a quality to be acceptable. What's the best way to do a high quality ImageData resize?
Edit: I'm scaling down.
AWT offers image scaling with different modes. For downscaling, Area Averaging offers the best quality. One could of course re-implement the area averaging scaling algorithm for SWT, or, for a quick solution which often suffices:
The code to convert between SWT and AWT images can be found here.
/**
* Resizes an image, using the given scaling factor. Constructs a new image resource, please take care of resource
* disposal if you no longer need the original one. This method is optimized for quality, not for speed.
*
* @param image source image
* @param scale scale factor (<1 = downscaling, >1 = upscaling)
* @return scaled image
*/
public static org.eclipse.swt.graphics.Image resize (org.eclipse.swt.graphics.Image image, float scale) {
int w = image.getBounds().width;
int h = image.getBounds().height;
// convert to buffered image
BufferedImage img = convertToAWT(image.getImageData());
// resize buffered image
int newWidth = Math.round(scale * w);
int newHeight = Math.round(scale * h);
// determine scaling mode for best result: if downsizing, use area averaging, if upsizing, use smooth scaling
// (usually bilinear).
int mode = scale < 1 ? BufferedImage.SCALE_AREA_AVERAGING : BufferedImage.SCALE_SMOOTH;
java.awt.Image scaledImage = img.getScaledInstance(newWidth, newHeight, mode);
// convert the scaled image back to a buffered image
img = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_RGB);
img.getGraphics().drawImage(scaledImage, 0, 0, null);
// reconstruct swt image
ImageData imageData = convertToSWT(img);
return new org.eclipse.swt.graphics.Image(Display.getDefault(), imageData);
}
public static BufferedImage convertToAWT (ImageData data) {
ColorModel colorModel = null;
PaletteData palette = data.palette;
if (palette.isDirect) {
colorModel = new DirectColorModel(data.depth, palette.redMask, palette.greenMask, palette.blueMask);
BufferedImage bufferedImage = new BufferedImage(colorModel, colorModel.createCompatibleWritableRaster(data.width, data.height),
false, null);
WritableRaster raster = bufferedImage.getRaster();
int[] pixelArray = new int[3];
for (int y = 0; y < data.height; y++) {
for (int x = 0; x < data.width; x++) {
int pixel = data.getPixel(x, y);
RGB rgb = palette.getRGB(pixel);
pixelArray[0] = rgb.red;
pixelArray[1] = rgb.green;
pixelArray[2] = rgb.blue;
raster.setPixels(x, y, 1, 1, pixelArray);
}
}
return bufferedImage;
} else {
RGB[] rgbs = palette.getRGBs();
byte[] red = new byte[rgbs.length];
byte[] green = new byte[rgbs.length];
byte[] blue = new byte[rgbs.length];
for (int i = 0; i < rgbs.length; i++) {
RGB rgb = rgbs[i];
red[i] = (byte) rgb.red;
green[i] = (byte) rgb.green;
blue[i] = (byte) rgb.blue;
}
if (data.transparentPixel != -1) {
colorModel = new IndexColorModel(data.depth, rgbs.length, red, green, blue, data.transparentPixel);
} else {
colorModel = new IndexColorModel(data.depth, rgbs.length, red, green, blue);
}
BufferedImage bufferedImage = new BufferedImage(colorModel, colorModel.createCompatibleWritableRaster(data.width, data.height),
false, null);
WritableRaster raster = bufferedImage.getRaster();
int[] pixelArray = new int[1];
for (int y = 0; y < data.height; y++) {
for (int x = 0; x < data.width; x++) {
int pixel = data.getPixel(x, y);
pixelArray[0] = pixel;
raster.setPixel(x, y, pixelArray);
}
}
return bufferedImage;
}
}
public static ImageData convertToSWT (BufferedImage bufferedImage) {
if (bufferedImage.getColorModel() instanceof DirectColorModel) {
DirectColorModel colorModel = (DirectColorModel) bufferedImage.getColorModel();
PaletteData palette = new PaletteData(colorModel.getRedMask(), colorModel.getGreenMask(), colorModel.getBlueMask());
ImageData data = new ImageData(bufferedImage.getWidth(), bufferedImage.getHeight(), colorModel.getPixelSize(), palette);
WritableRaster raster = bufferedImage.getRaster();
int[] pixelArray = new int[3];
for (int y = 0; y < data.height; y++) {
for (int x = 0; x < data.width; x++) {
raster.getPixel(x, y, pixelArray);
int pixel = palette.getPixel(new RGB(pixelArray[0], pixelArray[1], pixelArray[2]));
data.setPixel(x, y, pixel);
}
}
return data;
} else if (bufferedImage.getColorModel() instanceof IndexColorModel) {
IndexColorModel colorModel = (IndexColorModel) bufferedImage.getColorModel();
int size = colorModel.getMapSize();
byte[] reds = new byte[size];
byte[] greens = new byte[size];
byte[] blues = new byte[size];
colorModel.getReds(reds);
colorModel.getGreens(greens);
colorModel.getBlues(blues);
RGB[] rgbs = new RGB[size];
for (int i = 0; i < rgbs.length; i++) {
rgbs[i] = new RGB(reds[i] & 0xFF, greens[i] & 0xFF, blues[i] & 0xFF);
}
PaletteData palette = new PaletteData(rgbs);
ImageData data = new ImageData(bufferedImage.getWidth(), bufferedImage.getHeight(), colorModel.getPixelSize(), palette);
data.transparentPixel = colorModel.getTransparentPixel();
WritableRaster raster = bufferedImage.getRaster();
int[] pixelArray = new int[1];
for (int y = 0; y < data.height; y++) {
for (int x = 0; x < data.width; x++) {
raster.getPixel(x, y, pixelArray);
data.setPixel(x, y, pixelArray[0]);
}
}
return data;
}
return null;
}
The accepted solution doesn't deal with transparency. Here's a snippet I've came across that does hi-quality resize and preserves transparency as well:
public static Image resize(Image image, int width, int height) {
Image scaled = new Image(Display.getDefault(), width, height);
GC gc = new GC(scaled);
gc.setAntialias(SWT.ON);
gc.setInterpolation(SWT.HIGH);
gc.drawImage(image, 0, 0,image.getBounds().width, image.getBounds().height, 0, 0, width, height);
gc.dispose();
image.dispose(); // don't forget about me!
return scaled;
}
I've found it here:
We've had success with ImageMagick / JMagick. http://www.jmagick.org/index.html
The only problem is that if the images are user uploads, and you have a large user base, you will have memory leaks because of invalid image files and so on.
