java 处理图片为圆角，而且圆角要透明的，怎么做啊

Question

现在只能将图片变为圆角，但不是透明的，背景是白色的，
 BufferedImage image = ImageIO.read(imageFile);
    int w = image.getWidth(); 
        int h = image.getHeight(); 
        BufferedImage output = new BufferedImage(w, h, 
                BufferedImage.TYPE_INT_ARGB);          Graphics2D g2 = output.createGraphics();          
        // This is what we want, but it only does hard-clipping, i.e. aliasing 
        // g2.setClip(new RoundRectangle2D ...)          // so instead fake soft-clipping by first drawing the desired clip shape 
        // in fully opaque white with antialiasing enabled... 
        g2.setComposite(AlphaComposite.SrcOut); 
        //g2.setComposite(AlphaComposite.getInstance(AlphaComposite.DST, 0.0f)); 
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
                RenderingHints.VALUE_ANTIALIAS_ON); 
        g2.setColor(new Color(0,0,0)); 
        g2.setBackground(Color.black);  
            g2.setPaint(new Color(0,0,0));  
        g2.fill(new RoundRectangle2D.Float(0, 0, w, h, 60, 
                60)); 
        // ... then compositing the image on top, 
        // using the white shape from above as alpha source 
        g2.setComposite(AlphaComposite.SrcAtop); 
        g2.drawImage(image, 0, 0, null);          g2.dispose(); 
        
        
        
        ImageIO.write(output, "png", new File(filePath));

Answer 1

你可以了解下thumbnailator这个图片处理库https://github.com/coobird/thumbnailatorBufferedImage image = ImageIO.read(imageFile);
    int w = image.getWidth(); 
        int h = image.getHeight(); 
        BufferedImage output = new BufferedImage(w, h, 
                BufferedImage.TYPE_INT_ARGB);         Graphics2D g2 = output.createGraphics(); 
g2.setColor(new Color(0,0,0,0)); //用全透明颜色
g2.fillRect(0,0,w,h);//覆盖整个画布        // This is what we want, but it only does hard-clipping, i.e. aliasing 
        // g2.setClip(new RoundRectangle2D ...)         // so instead fake soft-clipping by first drawing the desired clip shape 
        // in fully opaque white with antialiasing enabled... 
        g2.setComposite(AlphaComposite.SrcOut); 
        //g2.setComposite(AlphaComposite.getInstance(AlphaComposite.DST, 0.0f)); 
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
                RenderingHints.VALUE_ANTIALIAS_ON); 
        g2.setColor(new Color(0,0,0)); 
        g2.setBackground(Color.black);  
            g2.setPaint(new Color(0,0,0));  
        g2.fill(new RoundRectangle2D.Float(0, 0, w, h, 60, 
                60)); 
        // ... then compositing the image on top, 
        // using the white shape from above as alpha source 
        g2.setComposite(AlphaComposite.SrcAtop); 
        g2.drawImage(image, 0, 0, null);         g2.dispose(); 
        
        
        
        ImageIO.write(output, "png", new File(filePath));

Answer 2

maven使用hutool自带的图像工具，首先pom.xml加
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>4.5.7</version>
        </dependency>
然后java代码读取上传图片
BufferedImage image = ImageIO.read(imageFile);
圆角处理
image = Img.from(image).round(0.05).getImg();
最后一定要使用png格式
ImageIO.write(output, "png", new File(filePath));

Answer 3

是不是透明和图片文件格式有关系，我所知道的只有psd格式（photoshop格式文件）和tif格式的图片才支持图层模式。其他格式会在保存时会强制合并图层，造成透明部分被填白色。改图片的推荐还是用专业软件比较好。