java - 抓取 SWT 组件的继承背景图像(滚动复合)

Question

我有一个带有背景图像的外壳。在这个外壳内，我有一个滚动的复合 Material 。这个滚动的合成继承了外壳的背景图像。

我想对滚动合成的继承背景图像执行某种 alpha 混合/渐变。

我遵循 here 中的代码.

1. 矩形 rect = sc.getClientArea();//此矩形始终返回宽度和高度为 0。
2. Image newImage = new Image(sc.getDisplay(), Math.max(1, rect.width), rect.height);//似乎没有抓取背景图像，即使我硬编码了宽度和高度。

这里有一些代码:

sc = new ScrolledComposite(parent, SWT.BORDER_SOLID | SWT.V_SCROLL);
sc.setExpandHorizontal(true);
sc.setExpandVertical(true);

sc.setAlwaysShowScrollBars(true);
sc.setMinWidth(0);

GridData gd = new GridData(GridData.FILL, GridData.FILL, true, true);
sc.setLayoutData(gd);
sc.setLayout(new GridLayout(1, false));

Rectangle rect = sc.getClientArea();
Image newImage = new Image(sc.getDisplay(), sc.getParent().getBackgroundImage(), SWT.IMAGE_COPY);
GC gc = new GC(newImage);

// need to do clipping on the image so that only the background underlying the scrolled composite gets the gradient

// fill background 
gc.setForeground(new Color(sc.getDisplay(), 100,200,123)); 
gc.setBackground(new Color(sc.getDisplay(), 23,23,23)); 
gc.fillGradientRectangle(rect.x, rect.y, rect.width, rect.height, true);  
gc.dispose();

sc.setBackgroundImage(newImage);
sc.setBackgroundMode(SWT.INHERIT_DEFAULT);


innerComposite = new Composite(sc, SWT.NONE);

GridLayout gl = new GridLayout();
gl.numColumns = 1;
innerComposite.setLayout(gl);
gd = new GridData(GridData.FILL_BOTH);
gd.grabExcessVerticalSpace = true;
innerComposite.setLayoutData(gd);

/**
* Creates other widgets here!
*/
sc.setContent(innerComposite);
sc.layout();

Answer 1

我在这里看到的一个逻辑问题是，您太早地完成了所有渐变工作。即使您执行类似这样的操作，也不意味着 shell 或窗口/复合本身已创建并准备就绪。一个非常方便的句柄是 Hook 到 SWT.Resize 事件。

无论如何，请检查以下代码:

输出

代码!!

注意您必须提供image.png

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.ScrolledComposite;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.layout.FormLayout;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;

public class ImageGradientTest {

    private Image imageGradient;
    private Image image;

    private void createComponents(Shell parent) 
    {
        ScrolledComposite sc = new ScrolledComposite(parent, SWT.BORDER_SOLID | SWT.V_SCROLL);
        sc.setExpandHorizontal(true);
        sc.setExpandVertical(true);

        sc.setAlwaysShowScrollBars(true);
        sc.setMinWidth(0);

        GridData gd = new GridData(GridData.FILL, GridData.FILL, true, true);
        sc.setLayoutData(gd);
        sc.setLayout(new GridLayout(1, false));


        final Composite composite = new Composite(sc, SWT.NONE);
        composite.addListener(SWT.Resize, new Listener() {
            public void handleEvent(Event e) {
                changeImage(composite);
            }
        });
        composite.setLayout(new FormLayout());
        composite.setBackgroundMode(SWT.INHERIT_DEFAULT);

        Label label = new Label(composite, SWT.None);
        label.setText("Hello, World!");

        sc.setContent(composite);
        sc.layout();

    }

    private void changeImage(Composite composite) 
    {
        Image oldImage = imageGradient;

        Display display = composite.getDisplay();
        Rectangle rect = composite.getClientArea();
        imageGradient = new Image(display, image, SWT.IMAGE_COPY);


        GC gc = new GC(imageGradient);
        Color color1 = new Color(display, 200, 200, 255);
        Color color2 = new Color(display, 255, 255, 255);

        gc.setAlpha(245);           // Two have a layer effect you should set the alpha
        gc.setForeground(color1);
        gc.setBackground(color2);
        gc.fillGradientRectangle(rect.x, rect.y, rect.width, rect.height, true);

        color2.dispose();
        color1.dispose();
        gc.dispose();


        composite.setBackgroundImage(imageGradient);

        if (oldImage != null) {
            oldImage.dispose();
        }
    }

    private void openShell() 
    {
        Display display = new Display();

        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());

        image = new Image(display, "image.png");

        shell.setBackgroundImage(image);
        shell.setBackgroundMode(SWT.INHERIT_DEFAULT);

        createComponents(shell);

        shell.open();

        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }

        image.dispose();
        imageGradient.dispose();        
        display.dispose();
    }

    public static void main(String[] args) {
        ImageGradientTest sweet = new ImageGradientTest();
        sweet.openShell();
    }
}

捕获客户区图像的代码!!

Display display = composite.getDisplay();
Rectangle rect = composite.getClientArea();
Image i = new Image(display, composite.getClientArea().width, composite.getClientArea().height);
GC gc = new GC(i);

composite.print(gc);            // This is important

ImageLoader loader = new ImageLoader();
loader.data = new ImageData[]{i.getImageData()};
loader.save("hello.png", SWT.IMAGE_PNG);

gc.dispose();
i.dispose();

尽管 check this link因为该方法不是跨平台的。