Java / ImageIO获取图像尺寸而不读取整个文件？

Question

有没有一种方法可以获取图像尺寸而无需读取整个文件？

URL url=new URL(<BIG_IMAGE_URL>);

BufferedImage img=ImageIO.read(url);

System.out.println(img.getWidth()+" "+img.getHeight());

img=null;

Answer 1

try(ImageInputStream in = ImageIO.createImageInputStream(resourceFile)){&nbsp; &nbsp; final Iterator<ImageReader> readers = ImageIO.getImageReaders(in);&nbsp; &nbsp; if (readers.hasNext()) {&nbsp; &nbsp; &nbsp; &nbsp; ImageReader reader = readers.next();&nbsp; &nbsp; &nbsp; &nbsp; try {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; reader.setInput(in);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return new Dimension(reader.getWidth(0), reader.getHeight(0));&nbsp; &nbsp; &nbsp; &nbsp; } finally {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; reader.dispose();&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }}&nbsp;

Answer 2

使用ImageReader.getHeight（int）和ImageReader.getWidth（int）通常仅读取图像标头（我在看JDK6源代码）。因此，ImageReader很可能是最佳选择。

Answer 3

您必须调查一下ImageReader.getImageMetadata()。不幸的是，Java Image API根本不易于使用。您可以在的软件包文档中找到元数据格式的说明javax.imageio.metadata。有一些更易于使用的第三方库，例如MediaUtil（最近更新3年，但对我来说效果很好）。