问题描述
大家好，每当我尝试使用 ImageIO.createImageInputStream 获取 ImageInputStream 对象时，它只会返回 null 而没有异常、警告或错误.我尝试将不同的数据类型传递给函数，一个简单的 File 和一个 InputStream，但都返回了 null.文档说，如果没有找到合适的 ImageInputStreamSpi 则该函数将返回 null，但该文件是沼泽标准的 JPEG，当然 Java 附带了一个服务提供者这种开箱即用的格式?感谢您抽出宝贵时间.
Hey all,Whenever I try to get an ImageInputStream object using ImageIO.createImageInputStream it simply returns null with no exceptions, warnings or errors. I have tried passing different data types to the function, a simple File, and an InputStream, but both returned null also. The documentation says that if no suitable ImageInputStreamSpi is found then the function will return null, but the file is a bog-standard JPEG, and surely Java comes with a service provider for such a format out of the box?Thanks for your time.
/**
* Reads in an image from a file and returns the image in a
* {@code BufferedImage} object.
*
* @param source the file to create the {@code BufferedImage}
* from.
* @return the {@code BufferedImage} object representing the image
* in {@code source}.
*/
private BufferedImage readImage( File source ) {
// There is only one image in this file
final int imageIndex = 0;
BufferedImage image = null;
try {
// Get the ImageReader object for this filetype
Iterator readers =
ImageIO.getImageReaders( source );
ImageReader reader = (ImageReader) readers.next();
// Create an ImageInputStream object from the source image file
ImageInputStream iis = ImageIO.createImageInputStream( source );
// Raises IllegalArgumentException, because iis is null
reader.setInput( iis, true );
// Read the image file
image = reader.read( imageIndex );
} catch ( Exception exception ) {
exception.printStackTrace();
System.exit( -1 );
}
return image;
}
推荐答案
你为什么要这么做??你可以简单地这样做:
Why are you doing all that??you can simply do this:
image = ImageIO.read(source);
没有 Iterators、ImageInputStreams...什么都没有！
No Iterators, ImageInputStreams... no nothing !
EDIT:既然你坚持，你的代码不起作用，因为你发送一个 File 到 ImageIO.getImageReaders() 而不是一个 ImageInputStream.所以你的代码应该是这样的:
EDIT: Since you insist, your code is not working because you're sending a File to ImageIO.getImageReaders() instead of a ImageInputStream. SO your code should look something like that:
ImageInputStream iis = ImageIO.createImageInputStream(source);
Iterator readers = ImageIO.getImageReaders(iis);
ImageReader reader = (ImageReader) readers.next();
reader.setInput(iis, false);
image = reader.read(imageIndex);
这篇关于ImageIO.createImageInputStream 不断返回 null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！