聊聊ImageIO使用argb操作jpg的bug

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

• JDK-4712797 : ImageIO fails to decode YCbCr JPEGs that do not have a JFIF marker
• JDK-4776576 : REG: ImageIO reader produces an incorrect image when read as a RenderedImage

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。

doc

• Colors appear wrong in image file if image type is TYPE_INT_ARGB and writing with ImageIO
• jpeg image color gets drastically changed after just ImageIO.read() and ImageIO.write()