使图像适合 JPanel

Question

我正在尝试缩放图像以使其始终适合我的 JPanel。不幸的是，使用这种方法我并不总是收到我想收到的图像。大多数情况下它是缩放的，我宁愿将整个图像缩放。

这就是创建图像的 class。 600 是面板宽度，400 是面板高度。

知道哪里出了问题吗？

public class Image extends Component{
    
    private BufferedImage img;
    protected int width;
    protected int height;
    private String path;

    @Override
    public void paint(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);

        double scale = getScale(600,400,img.getWidth(),img.getHeight());
        double xPos = (600 - scale * img.getWidth())/2;
        double yPos = (400 - scale *img.getHeight())/2;
        
        AffineTransform at = AffineTransform.getTranslateInstance(xPos, yPos);
        at.scale(scale, scale);
        g2.drawRenderedImage(img, at);
        System.out.println(scale);
        
    }

    public Image(String path){
        try{
            img = ImageIO.read(new File(path));
        } catch (IOException e) { }
        this.width=img.getWidth();
        this.height=img.getHeight();
        this.path = path;
    }
   
    
    public double getScale(int panelWidth, int panelHeight, int imageWidth, int imageHeight){
        double scale = 1;
        double xScale, yScale;
        
        if(imageWidth > panelWidth || imageHeight > panelHeight){
            xScale = (double)imageWidth/panelWidth;
            yScale = (double)imageHeight/panelHeight;
            scale = Math.max(xScale, yScale);
        }else if(imageWidth < panelWidth && imageHeight < panelHeight){
            xScale = (double)panelWidth/imageWidth;
            yScale = (double)panelHeight/imageHeight;
            scale = Math.max(xScale, yScale);
        }else{
            scale = 1;
        }
        return scale;
    }

Answer 1

如果您以正确的顺序执行操作，则不需要使用浮点数。假设imageWidth、imageHeight、panelWidth都是int:

// Calculate the width of the scaled image; if the image is wider than the 
// panel, use the panel width, otherwise use the image width (i.e. don't upscale)

int scaledWidth = Math.min(imageWidth, panelWidth);

// Given the scaled width, calculate the scaled height
// Force it to be at least 1 pixel, since if you have an image that's wider than
// the panel and only 1 pixel tall, this will scale to zero height, which you
// don't want

int scaledHeight = Math.max(1, imageHeight * scaledWidth / imageWidth);

以上假设您想要适应宽度，并且如果图像高度超过面板高度，将提供滚动机制。如果你想适应高度（和溢出的水平滚动），只需对变量进行必要的更改。

Answer 2

JPanel 是一个 Swing 组件，这意味着您正在使用 Swing。

对于自定义绘画，您应该扩展 JPanel 或 JComponent。大多数人使用 JPanel，因为它会为您清除组件的背景。

Swing 组件的自定义绘制是通过重写 paintComponent(...)

完成的

so it will always fit my JPanel

定义“适合”？

假设您正在尝试缩放图像以保留其原始比例，您可以这样做：

@Override
protected void paintComponent(Graphics g)
{
    super.paintComponent(g);

    double imageWidth = image.getWidth(null);
    double imageHeight = image.getHeight(null);
    double factor = Math.min(getWidth() / imageWidth, getHeight() / imageHeight);
    int width = (int)(image.getWidth(null) * factor);
    int height = (int)(image.getHeight(null) * factor);
    g.drawImage(image, 0, 0, width, height, this);
}

如果您只是想让图像适合面板，那么您可以：

@Override
protected void paintComponent(Graphics g)
{
    super.paintComponent(g);

    g.drawImage(image, 0, 0, getWidth(), getHeight(), this);
}

使图像适合 JPanel

Fit image into JPanel

java

swing

image

jpanel