关于java ByteArrayOutputStream类

发布于 2024-10-03 22:54:26 字数 441 浏览 6 评论 0原文

BufferedImage bufferedImage = ImageIO.read(new File("/...icon.jpg"));

// this writes the bufferedImage into a byte array called resultingBytes
ByteArrayOutputStream byteArrayOut = new ByteArrayOutputStream();

ImageIO.write(bufferedImage, "jpg", byteArrayOut);

byte[] resultingBytes = byteArrayOut.toByteArray();

我使用上面的代码获取 JEPG 图像作为字节数组。我想知道这个字节数组到底是什么。该数组是否包含任何文件头信息或仅包含像素值？例如，如果我想反转该图像的颜色，有什么好方法呢？非常感谢！

原文

BufferedImage bufferedImage = ImageIO.read(new File("/...icon.jpg"));

// this writes the bufferedImage into a byte array called resultingBytes
ByteArrayOutputStream byteArrayOut = new ByteArrayOutputStream();

ImageIO.write(bufferedImage, "jpg", byteArrayOut);

byte[] resultingBytes = byteArrayOut.toByteArray();

I use the above code to get a JEPG image as a byte array. I want to know what exactly is in this byte array. Does this array contain any file header information or just pixel values? And for example, if I want to reverse this image's color, what is a good way to do so?
Thanks so much!

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坏尐絯 2024-10-10 22:54:26

这是内存中的完整 JPEG 文件。

编辑：如果您想将像素数据作为数组进行操作，您可能会发现Raster更有帮助：

例如：

Raster raster = bufferedImage.getData();

然后您可以调用Raster.getPixels方法之一。

It's a complete JPEG file, in memory.

EDIT: If you want to manipulate pixel data as an array, you may find Raster more helpful:

E.g.:

Raster raster = bufferedImage.getData();

You can then call one of the Raster.getPixels methods.

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[浮城] 2024-10-10 22:54:26

ByteArrayOutputStream 包含您写入的所有内容。不多不少。所以你的问题实际上是关于 ImageIO.write() 的。它根据您提供的编码类型写出图像的编码。这是 JPEG。

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屌丝范 2024-10-10 22:54:26

以下是读取真实像素值的方法。 JPEG 信息更难处理！

public static void main(String... args) throws IOException {
    String u = "http://blog.stackoverflow.com/wp-content/uploads/stackoverflow-logo-300.png";

    BufferedImage old = ImageIO.read(new URL(u));
    BufferedImage inverted = new BufferedImage(old.getWidth(),
                                               old.getHeight(),
                                               BufferedImage.TYPE_INT_RGB);


    for (int y = 0; y < old.getHeight(); y++) {
        for (int x = 0; x < old.getWidth(); x++) {
            Color oldColor = new Color(old.getRGB(x, y));

            // reverse all but the alpha channel
            Color invertedColor = new Color(255 - oldColor.getRed(),
                                            255 - oldColor.getGreen(),
                                            255 - oldColor.getBlue());

            inverted.setRGB(x, y, invertedColor.getRGB());
        }
    }

    ImageIO.write(inverted, "png", new File("test.png"));
}

Here is how you read real pixel values. The JPEG information is much harder to do anything with!

public static void main(String... args) throws IOException {
    String u = "http://blog.stackoverflow.com/wp-content/uploads/stackoverflow-logo-300.png";

    BufferedImage old = ImageIO.read(new URL(u));
    BufferedImage inverted = new BufferedImage(old.getWidth(),
                                               old.getHeight(),
                                               BufferedImage.TYPE_INT_RGB);


    for (int y = 0; y < old.getHeight(); y++) {
        for (int x = 0; x < old.getWidth(); x++) {
            Color oldColor = new Color(old.getRGB(x, y));

            // reverse all but the alpha channel
            Color invertedColor = new Color(255 - oldColor.getRed(),
                                            255 - oldColor.getGreen(),
                                            255 - oldColor.getBlue());

            inverted.setRGB(x, y, invertedColor.getRGB());
        }
    }

    ImageIO.write(inverted, "png", new File("test.png"));
}

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