A more succinct way is to get the ImageWriter
directly from ImageIO
:
ImageWriter jpgWriter = ImageIO.getImageWritersByFormatName("jpg").next();
ImageWriteParam jpgWriteParam = jpgWriter.getDefaultWriteParam();
jpgWriteParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
jpgWriteParam.setCompressionQuality(0.7f);
ImageOutputStream outputStream = createOutputStream(); // For example implementations see below
jpgWriter.setOutput(outputStream);
IIOImage outputImage = new IIOImage(image, null, null);
jpgWriter.write(null, outputImage, jpgWriteParam);
jpgWriter.dispose();
The call to ImageWriteParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT)
is needed in order to explicitly set the compression’s level (quality).
In ImageWriteParam.setCompressionQuality()
1.0f
is maximum quality, minimum compression, while 0.0f
is minimum quality, maximum compression.
ImageWriter.setOutput
should be passed an ImageOutputStream
. While the method accepts Object
, according to documentation it’s usually not supported:
Use of a general
Object
other than anImageOutputStream
is intended for writers that interact directly with an output device or imaging protocol. The set of legal classes is advertised by the writer’s service provider’sgetOutputTypes
method; most writers will return a single-element array containing onlyImageOutputStream.class
to indicate that they accept only anImageOutputStream
.
Most cases should be handled by these two classes:
FileImageOutputStream
– an implementation ofImageOutputStream
that writes its output directly to aFile
orRandomAccessFile
.MemoryCacheImageOutputStream
– an implementation ofImageOutputStream
that writes its output to a regularOutputStream
. Usually used withByteArrayOutputStream
(thanks for the tip, @lmiguelmh!).