Question

我正在尝试在已就位图像的顶部绘制一个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的示例。这是产生的截图。

示例1（左上方）突出显示了我要解决的问题，我希望有2个圆或任何相交的形状/弧，它们都以相同的alpha等级绘制在一起，即没有因绘制而造成的复合不透明性彼此顶部。

示例3（左下）是我尝试解决的问题，方法是创建一个单独的带有实心形状的图像，然后使整个图像透明，我想发生的是，使用这种技术可以使图像在处理白色的情况下作为透明颜色，所以圆的边缘会与白色混合，以便在您绘制圆时会在形状周围产生“光晕”效果。

示例2（左上）通过将图像中的圆圈也绘制为透明的方式进一步突出了此问题，因此您可以看到由突出显示引起的更多粉红色。

我的问题是，在不了解背景色且没有关闭抗锯齿的情况下，如何获得想要的效果？有没有办法，因为我所有的研究都空白？也许我需要使用其他图像绘制解决方案并将其移植回SWT？我知道如果直接从文件加载该文件，它就能绘制透明图像，因此我知道它可以保存这种数据，但是如何创建它呢？

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

我使用Sean Bright此处描述的方法https://stackoverflow.com/a/15685473/6245535获得了预期的结果。

基本上：

我们创建图像src，并用gc用透明颜色填充图像
我们用纯色绘制椭圆形
我们得到了最终的图像数据：现在，图像（imageData.data）的像素数据数组也将包含alpha值，而图像（imageData.alphaData）的alpha数据数组是null
我们通过从imageData.alphaData中提取正确位置的alpha值来手动修复imageData.data；这部分假定我们正在使用32位深度的颜色；否则将无法正常工作
既然alphaData中的imageData是固定的，我们就用它创建一个图像processedImage
使用gc，我们最终绘制出processedImage并具有部分透明性

这是代码（这是肖恩的代码，有一些更改）：

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();

}

结果如下：

Answer 2

您可以使用Path将2个圆圈合并为一个实体，然后用透明颜色填充。

这是比我的previous answer简单得多的解决方案，并且没有光晕效果。

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：

使用SWT图形在另一张图像上绘制动态透明图像

2 个答案: