使图像适合 JPanel

问题描述

我正在尝试缩放图像，以便它始终适合我的 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，我宁愿拥有整个图像但缩放。

那是创建图像的类。 600 是 PanelWidth，400 是 PanelHeight。

知道出了什么问题吗？

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;
    }

解决方法

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 是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覆盖 paintComponent(...)

所以它总是适合我的 JPanel

定义“适合”？

假设您正在尝试缩放图像以保留其原始比例，您可以像这样：

@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,width,height,this);
}

如果您只是想使图像适合面板，那么您可以这样做：

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

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

,

如果您按正确的顺序进行操作，则不需要使用浮动。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，如果图像高度超过面板高度，将提供滚动机制。如果您想改为适合高度（以及水平滚动溢出），只需对变量进行必要的更改。