Re: [platform-swt-dev] Draw

[Carolyn_MacLeod@xxxxxxx]

Hi Maxine,
In future, please post user questions to the eclipse newsgroup.
This mailing list is for discussion on the implementation of SWT.
You can subscribe to the eclipse newsgroup by reading this page:
http://www.eclipse.org/newsgroups/index.html
and subscribing to this newsgroup:
news://www.eclipse.org/eclipse.tools

Having said that, here's a couple of code examples that should help.
Code example #1 will save to a file, but you may have trouble with your depth.
Currently, you can't save a 32-bit color depth BMP file using SWT.
And GIF can only be 8-bit color depth.
If you use an Image constructor, you get the default Display depth, which you quite likely have set to 32-bit (True color) in your Windows Control Panel.
So look quickly at code example #1 below, but you will probably want to have control over your image's depth and colors, so I recommend following code example #2. (Example #2 also shows how you would create a transparent gif, if that's what you wanted to do).

Code example #1:

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

public class ImageDrawTest {
        
public static void main (String [] args) {
        Display display = new Display();

        // create Image with default depth and palette
        Image image = new Image(display, 20, 20);
        
        // create a GC on your image to draw on it
        GC gc = new GC(image);
        gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
        gc.fillOval(2, 2, 16, 16);
        gc.dispose();

        // get ImageData from image
        ImageData imageData = image.getImageData();
        image.dispose();
        
        // save imageData as a BMP in current directory
        ImageLoader loader = new ImageLoader();
        loader.data = "">

new ImageData[] { imageData };
        loader.save("red_oval.bmp", SWT.IMAGE_BMP);

        display.dispose();
}
}

Code example #2:

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

public class ImageDrawTest2 {
       
public static void main (String [] args) {
        Display display = new Display();

        Color black = display.getSystemColor(SWT.COLOR_BLACK);
        Color white = display.getSystemColor(SWT.COLOR_WHITE);
        Color red = display.getSystemColor(SWT.COLOR_RED);
        Color transparent = display.getSystemColor(SWT.COLOR_BLUE);
        PaletteData palette = new PaletteData(new RGB[] {
                black.getRGB(),                        // 0
                white.getRGB(),                        // 1
                red.getRGB(),                        // 2
                transparent.getRGB()                // 3
        });
        ImageData imageData = new ImageData(20, 20, 4, palette); // depth 4, palette with 4 colors
        imageData.transparentPixel = 3; // if you want transparency, you would set that here
       
        // create your Image using your ImageData
        Image image = new Image(display, imageData);

        // create a GC on your image to draw on it
        GC gc = new GC(image);
        gc.setBackground(transparent);
        gc.fillRectangle(0, 0, 20, 20);
        gc.setBackground(red);
        gc.fillOval(2, 2, 16, 16);
        gc.setForeground(black);
        gc.drawLine(2, 2, 16, 16);
        gc.drawLine(2, 16, 16, 2);
        gc.dispose();

        // get modified ImageData from image
        imageData = image.getImageData();
        image.dispose();
       
        // save imageData as a GIF in current directory
        ImageLoader loader = new ImageLoader();
        loader.data = "">new ImageData[] { imageData };
        loader.save("red_oval.gif", SWT.IMAGE_GIF);

        display.dispose();
}
}

Carolyn

Jesse_Hill@xxxxxxx Sent by: platform-swt-dev-admin@xxxxxxxxxxx 05/13/02 09:00 PM Please respond to platform-swt-dev

To:        platform-swt-dev@xxxxxxxxxxx         cc:                 Subject:        Re: [platform-swt-dev] Draw

To draw on an image, you can do the following:

     Display display = new Display();
     Image image = new Image(display, 100, 100);
     GC gc = new GC(image);
     gc.drawLine(0, 0, 100, 100);
     gc.dispose();
     image.dispose();

You might be out of luck when it comes to writing the image to file. There
is API to do this:

     FileFormat.unloadIntoStream(ImageData data, LEDataOutputStream
stream);

but the file format classes are internal. Probably shouldn't be used.

You could get the data from the Image - Image.getImageData() - and write
that to a file yourself.

-Jesse



                                                                                                                               
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Hi There,

I need some documentation or a simple example of how I would go about
drawing a line on a image in swt and then saving that image to a file.

What should I draw on - canvas?

Regards,
Maxine.


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