使用SWT Graphics在另一个Image上绘制动态透明图像

Question

我试图在已经存在的图像的顶部绘制组合形状的透明蒙版。 我通过本文中包含的对话框代码提供了我正在尝试的技术示例。 这是它产生的截图。

示例1（左上角）突出显示我想要解决的问题，我希望有2个圆圈或任何相交的形状/弧线，所有绘制都与相同的alpha级别一起绘制，即没有因绘制顶部而导致的复合不透明度彼此。

示例3（左下角）是我尝试通过创建一个单独的图像和固体形状来解决问题，然后使整个图像透明，我认为使用这种技术会产生一个图像，其中白色被视为透明颜色，所以圆的边缘与白色混合，这样当你在它上面绘制时会在形状周围产生“晕”效果。

示例2（左上角）通过将图像中的圆圈绘制为透明来进一步突出显示此问题，因此您可以看到由突出显示引起的更粉红色。

我的问题是，如果不了解背景颜色，并且没有关闭抗锯齿，我怎样才能达到我想要的效果？ 有没有办法，因为我所有的研究都是空白的？ 也许我需要使用不同的图像绘制解决方案并返回SWT？ 我知道如果直接从文件加载它能够绘制透明图像，所以我知道它可以保存这种数据，但我该如何创建它？

import org.eclipse.jface.dialogs.Dialog;
import org.eclipse.swt.SWT;

import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class FMLDialog extends Dialog
{   
    private Color red;
    private Color blue;

    public FMLDialog(Shell parentShell)
    {
        super(parentShell);
    }



    @Override
    protected void configureShell(Shell shell)
    {
        red = new Color(shell.getDisplay(), new RGB(255,0,0));
        blue = new Color(shell.getDisplay(), new RGB(0,100,255));
        super.configureShell(shell);
        shell.setSize(new Point(450,550));
        shell.setText("FML");
    }   

    @Override
    public Control createDialogArea(final Composite comp)
    {

        Composite content = (Composite) super.createDialogArea(comp);
        Composite parent = new Composite(content, SWT.NONE);        

        GridLayout gridLayout2 = new GridLayout(1, false);
        parent.setLayout(gridLayout2);
        parent.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));           

        final Canvas c = new Canvas(parent, SWT.BORDER);
        c.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        c.addPaintListener(new PaintListener() {

            @Override
            public void paintControl(PaintEvent e) {
                e.gc.setAntialias(SWT.ON);
                drawFirstLayer(e.gc, 0, 0);
                drawFirstLayer(e.gc, 210, 0);
                drawFirstLayer(e.gc, 210, 210);
                drawFirstLayer(e.gc, 0, 210);

                drawSecondLayerTake1(e.gc, 0, 0);
                drawSecondLayerTake2(e.gc, 210, 0);
                drawSecondLayerTake3(e.gc, 0, 210);
                drawSecondLayerTake4(e.gc, 210, 210); 
            }
        });

        return content;     

    }

    private void drawFirstLayer(GC gc, int x, int y) {
        gc.setBackground(blue);
        gc.fillOval(x, y, 200 , 200);
    }

    private void drawSecondLayerTake1(GC gc, int x, int y) {
        // Simply draw 2 transparent circles
        // Issue here is the overlap between circles where the Alpha layers up
        gc.setAlpha(100);
        gc.setBackground(red);
        gc.fillOval(x + 70, y + 70, 60 , 60);
        gc.fillOval(x + 100, y + 100, 60 , 60);
        gc.setAlpha(255);
    }

    private void drawSecondLayerTake2(GC gc, int x, int y) {
        // Create an image with 2 transparent circles
        // Issue here is the overlap between circles where the Alpha layers up from the first
        // PLUS becasue my transparent colour is fixed to white the alpa on the circles is blended in to the white
        final Image src = new Image(null, 300, 300);
        final ImageData imageData = src.getImageData();
        imageData.transparentPixel = imageData.getPixel(0, 0);
        src.dispose();
        final Image processedImage = new Image(Display.getCurrent(), imageData);
        final GC imageGC = new GC(processedImage);      
        imageGC.setAntialias(SWT.ON);
        imageGC.setAlpha(100);
        imageGC.setBackground(red);
        imageGC.fillOval(70, 70, 60 , 60);
        imageGC.fillOval(100, 100, 60 , 60);
        imageGC.dispose();

        gc.drawImage(processedImage, x + 0, y + 0);

    }

    private void drawSecondLayerTake3(GC gc, int x, int y) {
        // Create an image with 2 solid circles, then draw that image on to the canvas with Alpha values.
        // Overlap issue goes away because the whole image is being made transparent together HOWEVER
        // there is a Halo effect around the edge of the red where the original circles were antialiased to blend into the "white"
        // background.

        final Image src = new Image(null, 300, 300);
        final ImageData imageData = src.getImageData();
        imageData.transparentPixel = imageData.getPixel(0, 0);
        src.dispose();
        final Image processedImage = new Image(Display.getCurrent(), imageData);
        final GC imageGC = new GC(processedImage);      
        imageGC.setAntialias(SWT.ON);
        imageGC.setBackground(red);
        imageGC.fillOval(70, 70, 60 , 60);
        imageGC.fillOval(100, 100, 60 , 60);
        imageGC.dispose();

        gc.setAlpha(100);
        gc.drawImage(processedImage, x + 0, y + 0);

    }

    private void drawSecondLayerTake4(GC gc, int x, int y) {
        // I need this one to draw like take 3 but without the white "halo" effect on the edge
        // How?!
    }

    public static void main(String[] args) {
        Display d = new Display();
        Shell s = new Shell();

        FMLDialog fml = new FMLDialog(s);
        fml.open();
    }

}

Answer 1

我能够使用Sean Bright描述的方法获得所需的结果： https ： //stackoverflow.com/a/15685473/6245535 。

基本上：

1. 我们创建一个图像src ，用gc我们用透明颜色填充它
2. 我们用纯色画椭圆形
3. 我们得到了得到的图像数据：现在，图像的像素数据数组（ imageData.data ）也将包含alpha值，而图像的alpha数据数组（ imageData.alphaData ）为null
4. 我们手动修复imageData.alphaData通过提取在从右侧位置上的阿尔法值imageData.data ; 这部分假设我们正在使用32位深度的颜色; 它不会起作用
5. alphaData imageData的alphaData是固定的，我们用它创建一个图像processedImage
6. 使用gc我们最终绘制具有部分透明度的processedImage

这是代码（这是Sean的代码，有一些变化）：

private void drawSecondLayerTake4(GC gc, int x, int y) {

    final int width = 300;
    final int height = 300;

    final Image src = new Image(null, width, height);

    final GC imageGC = new GC(src);

    imageGC.setAntialias(SWT.ON);

    // This sets the alpha on the entire canvas to transparent
    imageGC.setAlpha(0);
    imageGC.fillRectangle(0, 0, width, height);

    // Reset our alpha and draw the ovals
    imageGC.setAlpha(255);
    imageGC.setBackground(red);
    imageGC.fillOval(70, 70, 60, 60);
    imageGC.fillOval(100, 100, 60, 60);

    // We're done with the GC, so dispose of it
    imageGC.dispose();

    final ImageData imageData = src.getImageData();
    imageData.alphaData = new byte[width * height];

    // This is the hacky bit that is making assumptions about
    // the underlying ImageData.  In my case it is 32 bit data
    // so every 4th byte in the data array is the alpha for that
    // pixel...
    for (int idx = 0; idx < (width * height); idx++) {
        final int coord = (idx * 4) + 3;
        imageData.alphaData[idx] = imageData.data[coord];
    }

    // Now that we've set the alphaData, we can create our
    // final image
    final Image processedImage = new Image(Display.getCurrent(), imageData);

    gc.setAlpha(100);
    gc.drawImage(processedImage, x + 0, y + 0);

    // And get rid of the canvas
    src.dispose();

}

这是结果：

Answer 2

您可以使用Path合并单个实体中的2个圆，然后使用透明颜色填充它。

这是一个比我之前的答案简单得多的解决方案，没有光环效应。

代码：

private void drawSecondLayerTake4(GC gc, int x, int y) {

    final Path path = new Path(Display.getCurrent());
    path.addArc(x + 70, y + 70, 60, 60, 0, 360);
    path.addArc(x + 100, y + 100, 60, 60, 0, 360);

    gc.setAlpha(100);
    gc.setBackground(red);

    // needed to avoid holes in the path
    gc.setFillRule(SWT.FILL_WINDING);

    gc.fillPath(path);

    path.dispose();
}

结果如下：