TwelveMonkeys ImageIO 通过 javax.imageio.* 包的插件为 Java 平台提供扩展图像文件格式支持。
注意，GIF、 PNG 和 WBMP 格式已经通过 ImageIO API 支持，使用的是 JDK 标准插件。对于 BMP、 JPEG 和 TIFF 格式，TwelveMonkeys 插件提供了扩展格式支持和其他特性。
Basic usage
大多数时候，你所需要做的只是在你的项目中包含插件，然后写下:
BufferedImage image = ImageIO.read(file);
这将把文件的第一个图像完全加载到内存中。
最基本和最简单的书写形式是:
if (!ImageIO.write(image, format, file)) {
// Handle image not written case
}
这将使用给定格式的默认设置将整个图像写入单个文件。
这些插件在运行时会被自动发现。查看 FAQ 了解更多关于这种机制如何工作的信息。
Maven dependency example
To depend on the JPEG and TIFF plugin using Maven, add the following to your POM:
...
<dependencies>
...
<dependency>
<groupId>com.twelvemonkeys.imageio</groupId>
<artifactId>imageio-jpeg</artifactId>
<version>3.8.1</version>
</dependency>
<dependency>
<groupId>com.twelvemonkeys.imageio</groupId>
<artifactId>imageio-tiff</artifactId>
<version>3.8.1</version>
</dependency>
<!--
Optional dependency. Needed only if you deploy ImageIO plugins as part of a web app.
Make sure you add the IIOProviderContextListener to your web.xml, see above.
-->
<dependency>
<groupId>com.twelvemonkeys.servlet</groupId>
<artifactId>servlet</artifactId>
<version>3.8.1</version>
</dependency>
<!--
Or Jakarta version, for Servlet API 5.0
-->
<dependency>
<groupId>com.twelvemonkeys.servlet</groupId>
<artifactId>servlet</artifactId>
<version>3.8.1</version>
<classifier>jakarta</classifier>
</dependency>
</dependencies>
最终我的 MyImageIO 增强类。其实也是为了解决某些情况下 jpg 图片 ImageIO.read() 方法报错的问题。我寻找原因，发现用 jdk 自带的 jpeg 解析器不能解析所有的jpeg格式文件(如cmyk)。出现 unsupported formate 错误。之后使用 createJPEG4 解决了此问题，但是最终生成的图片有红屏现象，最终使用 TwelveMonkeys ImageIO 是无入侵且完美解决，这个值得点赞。
static class MyImageIO {
public static BufferedImage read(File input) throws IOException {
if (input == null) {
throw new IllegalArgumentException("input == null!");
}
if (!input.canRead()) {
throw new IIOException("Can't read input file!");
}
ImageInputStream stream = ImageIO.createImageInputStream(input);
if (stream == null) {
throw new IIOException("Can't create an ImageInputStream!");
}
BufferedImage bi = read(stream);
if (bi == null) {
stream.close();
}
return bi;
}
private static BufferedImage read(ImageInputStream stream)
throws IOException {
if (stream == null) {
throw new IllegalArgumentException("stream == null!");
}
Iterator<ImageReader> iter = ImageIO.getImageReaders(stream);
if (!iter.hasNext()) {
return null;
}
final ImageReader reader = iter.next();
ImageReadParam param = reader.getDefaultReadParam();
reader.setInput(stream, true, true);
BufferedImage bi;
try {
bi = reader.read(0, param);
} catch (IIOException e) {
Raster raster = reader.readRaster(0, null);
bi = createJPEG4(raster);
} finally {
reader.dispose();
stream.close();
}
return bi;
}
private static BufferedImage createJPEG4(Raster raster) {
int w = raster.getWidth();
int h = raster.getHeight();
byte[] rgb = new byte[w * h * 3];
// 彩色空间转换
float[] Y = raster.getSamples(0, 0, w, h, 0, (float[]) null);
float[] Cb = raster.getSamples(0, 0, w, h, 1, (float[]) null);
float[] Cr = raster.getSamples(0, 0, w, h, 2, (float[]) null);
float[] K = raster.getSamples(0, 0, w, h, 3, (float[]) null);
for (int i = 0, imax = Y.length, base = 0; i < imax; i++, base += 3) {
float k = 220 - K[i], y = 255 - Y[i], cb = 255 - Cb[i], cr = 255 - Cr[i];
double val = y + 1.402 * (cr - 128) - k;
val = (val - 128) * .65f + 128;
rgb[base] = val < 0.0 ? (byte) 0 : val > 255.0 ? (byte) 0xff
: (byte) (val + 0.5);
val = y - 0.34414 * (cb - 128) - 0.71414 * (cr - 128) - k;
val = (val - 128) * .65f + 128;
rgb[base + 1] = val < 0.0 ? (byte) 0 : val > 255.0 ? (byte) 0xff
: (byte) (val + 0.5);
val = y + 1.772 * (cb - 128) - k;
val = (val - 128) * .65f + 128;
rgb[base + 2] = val < 0.0 ? (byte) 0 : val > 255.0 ? (byte) 0xff
: (byte) (val + 0.5);
}
raster = Raster.createInterleavedRaster(new DataBufferByte(rgb,
rgb.length), w, h, w * 3, 3, new int[] { 0, 1, 2 }, null);
ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_sRGB);
ColorModel cm = new ComponentColorModel(cs, false, true,
Transparency.OPAQUE, DataBuffer.TYPE_BYTE);
return new BufferedImage(cm, (WritableRaster) raster, true, null);
}
}
参考
haraldk/TwelveMonkeys: TwelveMonkeys ImageIO: Additional plug-ins and extensions for Java's ImageIO https://github.com/haraldk/TwelveMonkeys
