Java 如何将 BufferedImage 转换为 InputStream？
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How to convert BufferedImage to InputStream?
提问by
I am uploading images using servlet. To perform resize operations i am converting InputStream to BufferedImage. Now i want to save it in mongoDB. Since, i am new to mongoDB as far as i know, GridFS takes InputStream.
我正在使用 servlet 上传图像。为了执行调整大小操作，我将 InputStream 转换为 BufferedImage。现在我想将它保存在 mongoDB 中。因为，据我所知，我是 mongoDB 的新手，GridFS 采用 InputStream。
So, is there any way to convert BufferedImage to InputStream?
那么，有没有办法将BufferedImage 转换为InputStream？
采纳答案by SLaks
You need to save the BufferedImage to a ByteArrayOutputStreamusing the ImageIOclass, then create a ByteArrayInputStreamfrom toByteArray().
您需要ByteArrayOutputStream使用ImageIO类将 BufferedImage 保存到 a ，然后创建一个ByteArrayInputStreamfrom toByteArray()。
回答by Edward83
First of all you must get your "bytes":
首先，你必须得到你的“字节”：
byte[] buffer = ((DataBufferByte)(bufferedImage).getRaster().getDataBuffer()).getData();
And then use ByteArrayInputStream(byte[] buf)constructor to create your InputStream;
然后使用ByteArrayInputStream(byte[] buf)构造函数来创建您的 InputStream；
回答by Igor
By overriding the method toByteArray(), returning the bufitself (not copying), you can avoid memory related problems. This will share the same array, and not creating another of the correct size. The important thing is to use the size()method in order to control the number of valid bytes into the array.
通过覆盖方法toByteArray()，返回buf自身（而不是复制），您可以避免与内存相关的问题。这将共享相同的数组，而不是创建另一个正确大小的数组。重要的是使用该size()方法来控制进入数组的有效字节数。
final ByteArrayOutputStream output = new ByteArrayOutputStream() {
@Override
public synchronized byte[] toByteArray() {
return this.buf;
}
};
ImageIO.write(image, "png", output);
return new ByteArrayInputStream(output.toByteArray(), 0, output.size());
回答by Sorter
BufferedImage? ByteArrayOutputStream? byte[]? ByteArrayInputStream
BufferedImage? ByteArrayOutputStream? byte[]?ByteArrayInputStream
Use the ImageIO.writemethod to make a BufferedImage(which is a RenderedImage) into a ByteArrayOutputStream. From there get a byte array (byte[]), feeding that into an InputStreamof type ByteArrayInputStream.
使用该ImageIO.write方法将 a BufferedImage（即 a RenderedImage）变成 a ByteArrayOutputStream。从那里得到一个字节数组 ( byte[])，将它输入到InputStream类型中ByteArrayInputStream。
ByteArrayOutputStream os = new ByteArrayOutputStream();
ImageIO.write(buffImage, "jpeg", os); // Passing: ?(RenderedImage im, String formatName, OutputStream output)
InputStream is = new ByteArrayInputStream(os.toByteArray());
Both the ByteArrayOutputStreamand InputStreamimplement AutoCloseable. So you can conveniently have those closed automatically by using try-with-resourcessyntax.
无论是ByteArrayOutputStream和InputStream落实AutoCloseable。因此，您可以使用try-with-resources语法方便地自动关闭它们。
