是的,可以从(单个)InputStream读取多个图像.

我认为最明显的解决方案是使用一种文件格式,该文件格式已广泛支持多种图像,例如TIFF.即使ImageIO类没有任何便利的方法,如ImageIO.read(…)/ ImageIO.write(…),javax.imageio API也对读取和写入多图像文件提供了良好的支持. )读取/写入单个图像的方法.这意味着您需要编写更多代码(下面的代码示例).

但是,如果输入是由控件之外的第三方创建的,则不能选择使用其他格式.从注释中可以看出,您的输入实际上是串联的Exif JPEG流.好消息是,Java的JPEGImageReader / Writer确实允许在同一流中包含多个JPEG,即使这种格式不是很常见.

要从同一流中读取多个JPEG,可以使用以下示例(请注意,该代码是完全通用的,并且可以读取其他多图像文件,例如TIFF)：

File file = ...; // May also use InputStream here

List images = new ArrayList<>();

try (ImageInputStream in = ImageIO.createImageInputStream(file)) {

Iterator readers = ImageIO.getImageReaders(in);

if (!readers.hasNext()) {

throw new AssertionError("No reader for file " + file);

}

ImageReader reader = readers.next();

reader.setInput(in);

// It's possible to use reader.getNumImages(true) and a for-loop here.

// However, for many formats, it is more efficient to just read until there's no more images in the stream.

try {

int i = 0;

while (true) {

images.add(reader.read(i++));

}

}

catch (IndexOutOfBoundsException expected) {

// We're done

}

reader.dispose();

}

此行以下的任何内容都只是额外的信息.

这是使用ImageIO API编写多图像文件的方法(代码示例使用TIFF,但是它非常通用,并且理论上也应适用于其他格式,但压缩类型参数除外).

File file = ...; // May also use OutputStream/InputStream here

List images = new ArrayList<>(); // Just add images...

Iterator writers = ImageIO.getImageWritersByFormatName("TIFF");

if (!writers.hasNext()) {

throw new AssertionError("Missing plugin");

}

ImageWriter writer = writers.next();

if (!writer.canWriteSequence()) {

throw new AssertionError("Plugin doesn't support multi page file");

}

ImageWriteParam param = writer.getDefaultWriteParam();

param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);

param.setCompressionType("JPEG"); // The allowed compression types may vary from plugin to plugin

// The most common values for TIFF, are NONE, LZW, Deflate or Zip, or JPEG

try (ImageOutputStream out = ImageIO.createImageOutputStream(file)) {

writer.setOutput(out);

writer.prepareWriteSequence(null); // No stream metadata needed for TIFF

for (BufferedImage image : images) {

writer.writeToSequence(new IIOImage(image, null, null), param);

}

writer.endWriteSequence();

}

writer.dispose();

请注意,在Java 9之前,您还需要第三方TIFF插件(例如JAI或我自己的TwelveMonkeys ImageIO)才能使用ImageIO读取/写入TIFF.

如果您真的不喜欢编写此冗长的代码,另一种选择是将图像包装成您自己的最小容器格式,该格式至少(包括)每个图像的长度.然后,您可以使用ImageIO.write(…)进行写入,也可以使用ImageIO.read(…)进行读取,但是您需要围绕它实现一些简单的流逻辑.当然,反对它的主要论据是它将是完全专有的.

但是,如果您要在类似客户端/服务器的设置中异步读取/写入(就像我怀疑的那样,从我的问题来看),这可能是很合理的,并且可能是可以接受的折衷方案.

就像是：

File file = new File(args[0]);

List images = new ArrayList<>();

try (DataOutputStream out = new DataOutputStream(new FileOutputStream(file))) {

ByteArrayOutputStream buffer = new ByteArrayOutputStream(1024 * 1024); // Use larger buffer for large images

for (BufferedImage image : images) {

buffer.reset();

ImageIO.write(image, "JPEG", buffer); // Or PNG or any other format you like, really

out.writeInt(buffer.size());

buffer.writeTo(out);

out.flush();

}

out.writeInt(-1); // EOF marker (alternatively, catch EOFException while reading)

}

// And, reading back:

try (DataInputStream in = new DataInputStream(new FileInputStream(file))) {

int size;

while ((size = in.readInt()) != -1) {

byte[] buffer = new byte[size];

in.readFully(buffer); // May be more efficient to create a FilterInputStream that counts bytes read, with local EOF after size

images.add(ImageIO.read(new ByteArrayInputStream(buffer)));

}

}

PS：如果您要做的只是将收到的图像写入磁盘,则不应使用ImageIO.而是使用普通的I / O(假定来自上一个示例的格式)：

try (DataInputStream in = new DataInputStream(new FileInputStream(file))) {

int counter = 0;

int size;

while ((size = in.readInt()) != -1) {

byte[] buffer = new byte[size];

in.readFully(buffer);

try (FileOutputStream out = new FileOutputStream(new File("pics/out/" + (counter++) +".jpeg"))) {

out.write(buffer);

out.flush();

}

}

}