/**
* 1、�?过ImageIO获得ImageReader 2、�?过ImageReader获得ImageInputStream 3、指定ImageReader的source 4、获得缩略图的数�?
* 5、若缩略图大�?，读取缩略图
*/
@Test
public void thumbnailTest() throws IOException {
Iterator<ImageReader> itr = ImageIO.getImageReadersByFormatName("jpg");
ImageReader imageReader = itr.next();
ImageInputStream imageInputStream = ImageIO.createImageInputStream(new File(SRCIMG));
imageReader.setInput(imageInputStream, true);
int thumbnailNum = imageReader.getNumThumbnails(0);
System.out.println(thumbnailNum);
if (thumbnailNum > 0) {
BufferedImage bufferedImage = imageReader.readThumbnail(0, 0);
// TODO 图片其它处理
System.out.println(bufferedImage.getWidth());
}
}
/**
* Creates a scaled version of the image provided by the specified input stream. This method tries
* to use thumbnails in the original image: If none fits, the full image is read and scaled.
*/
public static BufferedImage createScaledImage(
InputStream aInputStream, int aMaxSize, boolean aWithAlpha, Object aInterpolationQuality)
throws IOException {
ImageInputStream theImageInputStream = ImageIO.createImageInputStream(aInputStream);
Iterator<ImageReader> theImageReaders = ImageIO.getImageReaders(theImageInputStream);
ImageReader theReader;
if (theImageReaders.hasNext()) theReader = theImageReaders.next();
else return null;
theReader.setInput(theImageInputStream);
BufferedImage theOriginalImage = null;
if (theReader.readerSupportsThumbnails()) {
// Find the most suitable thumbnail, ie. the smallest that is bigger than requested size.
int theThumbnailsCount = theReader.getNumThumbnails(0);
int theFittest = -1; // Which is the fittest thumbnail?
int theFittestScore = Integer.MAX_VALUE; // Score of the current fittest. Lower is better.
for (int i = 0; i < theThumbnailsCount; i++) {
int theW = theReader.getThumbnailWidth(0, i);
int theH = theReader.getThumbnailHeight(0, i);
int theScore;
if (theW < aMaxSize & theH < aMaxSize) theScore = Integer.MAX_VALUE;
else theScore = Math.max(theW, theH) - aMaxSize;
if (theScore < theFittestScore) {
theFittest = i;
theFittestScore = theScore;
if (theScore == 0) break; // Can't improve, so don't iterate any more.
}
}
// Get the thumbnail
if (theFittest >= 0) theOriginalImage = theReader.readThumbnail(0, theFittest);
}
// Fallback if no thumbnail is found
if (theOriginalImage == null) theOriginalImage = theReader.read(0);
return createScaledImage(theOriginalImage, aMaxSize, aWithAlpha, aInterpolationQuality);
}