java 使用 ImageIO.read 的问题
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Problem using ImageIO.read
提问by Marquinio
Ok I have an Image that I'm trying to read. Problem is that the Image.read(file) returns NULL.
好的，我有一张我正在尝试阅读的图片。问题是 Image.read(file) 返回 NULL。
File file = new File("C:\images\image1.jpg");
if(file.exists()){
System.out.println("Image file exists.");
BufferedImage originalImage = ImageIO.read(file);
}
So image exists but ImageIO.read(file) returns NULL. No thrown errors nothing!!! Whats going on?
所以图像存在但 ImageIO.read(file) 返回 NULL。没有抛出错误什么都没有！！！这是怎么回事？
This is what I have tried so far:
这是我迄今为止尝试过的：
- Ok my environment is Windows 7. I tested with one of those images that comes with Windows and its able to read the image.
- The image1.jpg was created by another system. Now sure what method they are using.
- I tried converting the image into RGB as suggested here link textbut it fails with "Not a JPEG file: starts with 0x4d 0x4d".
- The image extension is .jpg, but windows says its a JPEG type? This is confusing.
- 好的，我的环境是 Windows 7。我用 Windows 附带的那些图像之一进行了测试，它能够读取图像。
- image1.jpg 是由另一个系统创建的。现在确定他们正在使用什么方法。
- 我尝试按照此处链接文本的建议将图像转换为 RGB， 但失败并显示“不是 JPEG 文件：以 0x4d 0x4d 开头”。
- 图像扩展名为 .jpg，但 windows 说它是 JPEG 类型？这令人困惑。
Can someone help with this? I'm new to this, not sure how to fix this.
有人可以帮忙吗？我是新手，不知道如何解决这个问题。
Ok I just figured out that ImageIO.getImageReaders(stream) returns an empty Iterator. This means that it couldn't find a suitable reader? How am I supposed to read this image?
好的，我刚刚发现 ImageIO.getImageReaders(stream) 返回一个空的迭代器。这意味着它找不到合适的阅读器？我应该如何阅读这张图片？
采纳答案by Marquinio
Ok since I switched laptops, I looked at my old laptop and found this JAR jai-imageio.jar in the jre/ext/lib (I know bad idea). I moved it to my project/lib and it worked! I guess this jai-imageio.jar contains additional image readers.
好的，因为我换了笔记本电脑，我看了看我的旧笔记本电脑，在 jre/ext/lib 中找到了这个 JAR jai-imageio.jar（我知道这个主意不好）。我把它移到了我的项目/库中，它起作用了！我猜这个 jai-imageio.jar 包含额外的图像阅读器。
回答by Jason
From the Javadocs for ImageIO.read()
来自 Javadocs ImageIO.read()
Returns a
BufferedImageas the result of decoding a supplied File with anImageReaderchosen automatically from among those currently registered. TheFileis wrapped in anImageInputStream. If no registeredImageReaderclaims to be able to read the resulting stream,nullis returned.
返回 a
BufferedImage作为解码提供的 File 的结果，并ImageReader从当前注册的文件中自动选择一个 。该File被包裹在一个ImageInputStream。如果没有注册的ImageReader声明能够读取结果流，null则返回。
Try creating an ImageInputStream, then pass that onto the ImageIO.read()method, instead of sending the file itself.
尝试创建一个ImageInputStream，然后将其传递给ImageIO.read()方法，而不是发送文件本身。
回答by Sanjeev
Awesome, I had the same problem, wherein it was supporting 24 image formats in eclipse but was supporting only 12 image formats in command prompt with maven. Once I placed jai_imageio.jar in maven's test path, maven has begun to support 24 image formats as well.
太棒了，我遇到了同样的问题，它在 eclipse 中支持 24 种图像格式，但在 maven 的命令提示符中仅支持 12 种图像格式。一旦我将 jai_imageio.jar 放在 maven 的测试路径中，maven 也开始支持 24 种图像格式。
