序

本文主要来聊一下使用ImageIO在BufferedImage.TYPE_INT_ARGB模式下操作jpg格式图片显示黑色的bug。

bug

复现实例

public void testArgbOnJpg() throws IOException {        int width = 400;        int height = 400;        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);        Graphics2D g2 = image.createGraphics();        g2.setColor(Color.WHITE);        g2.fillRect(0, 0, width, height);        g2.setComposite(AlphaComposite.Src);        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);                g2.setColor(Color.RED);        Ellipse2D.Float shape = new Ellipse2D.Float(20, 20, 10, 10);        g2.fill(shape);        g2.dispose();        image.flush();        ImageIO.write(image,"jpg",new File("out.jpg"));    }

可以发现输出的图片黑屏。

修复

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

jpg情况下，改为使用BufferedImage.TYPE_INT_RGB，即可正常显示。

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