How to display system icon for a file in SWT?

问题:

I want to display a file tree similarly to java2s.com 'Create a lazy file tree', but include the actual system icons - especially for folders. SWT does not seem to offer this (Program API does not support folders), so I came up with the following:

public Image getImage(File file)
{
    ImageIcon systemIcon = (ImageIcon) FileSystemView.getFileSystemView().getSystemIcon(file);
    java.awt.Image image = systemIcon.getImage();

    int width = image.getWidth(null);
    int height = image.getHeight(null);
    BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2d = bufferedImage.createGraphics();
    g2d.drawImage(image, 0, 0, null);
    g2d.dispose();
    int[] data = ((DataBufferInt) bufferedImage.getData().getDataBuffer()).getData();
    ImageData imageData = new ImageData(width, height, 24, new PaletteData(0xFF0000, 0x00FF00, 0x0000FF));
    imageData.setPixels(0, 0, data.length, data, 0);
    Image swtImage = new Image(this.display, imageData);
    return swtImage;
}

However, the regions that should be transparent are displayed in black. How do I get this working, or is there another approach I should take?

Update:

I think the reason is that PaletteData is not intended for transparency at all.

For now, I fill the BufferedImage with Color.WHITE now, which is an acceptable workaround. Still, I'd like to know the real solution here...

回答1:

You need a method like the following, which is a 99% copy from http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet156.java?view=co :

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);
        for (int y = 0; y < data.height; y++) {
            for (int x = 0; x < data.width; x++) {
                int rgb = bufferedImage.getRGB(x, y);
                int pixel = palette.getPixel(new RGB((rgb >> 16) & 0xFF, (rgb >> 8) & 0xFF, rgb & 0xFF)); 
                data.setPixel(x, y, pixel);
                if (colorModel.hasAlpha()) {
                    data.setAlpha(x, y, (rgb >> 24) & 0xFF);
                }
            }
        }
        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;
}

Then you can call it like:

static Image getImage(File file) {
    ImageIcon systemIcon = (ImageIcon) FileSystemView.getFileSystemView().getSystemIcon(file);
    java.awt.Image image = systemIcon.getImage();
    if (image instanceof BufferedImage) {
        return new Image(display, convertToSWT((BufferedImage)image));
    }
    int width = image.getWidth(null);
    int height = image.getHeight(null);
    BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2d = bufferedImage.createGraphics();
    g2d.drawImage(image, 0, 0, null);
    g2d.dispose();
    return new Image(display, convertToSWT(bufferedImage));
}

回答2:

For files, you can use org.eclipse.swt.program.Program to obtain an icon (with correct set transparency) for a given file ending:

File file=...
String fileEnding = file.getName().substring(file.getName().lastIndexOf('.'));
ImageData iconData=Program.findProgram(fileEnding ).getImageData();
Image icon= new Image(Display.getCurrent(), iconData);

For folders, you might consider just using a static icon.

回答3:

I haven't looked at the code in detail, but I notice you are using TYPE_INT_RGB instead of TYPE_INT_ARGB (which includes alpha/transparency support).

---

Looking at Snippet32 on the Eclipse site, I can see that you can usually pick up icons using the Program class. Using the extension ".Folder" doesn't seem to return an instance, even though it is a member of getExtensions().

This code can get a folder icon:

Display display = new Display();
Shell shell = new Shell(display);
Label label = new Label(shell, SWT.NONE);
label.setText("Can't find icon");
Image image = null;
for (Program p : Program.getPrograms()) {
  if ("Folder".equals(p.getName())) {
    ImageData data = p.getImageData();
    if (data != null) {
      image = new Image(display, data);
      label.setImage(image);
    }
    break;
  }
}
label.pack();
shell.pack();
shell.open();
while (!shell.isDisposed()) {
  if (!display.readAndDispatch())
    display.sleep();
}
if (image != null)
  image.dispose();
display.dispose();

That code needs refined, I think, but should be a pointer in the right direction. I only tested on English-language Windows XP.