从文件读取/写入图像到BufferedImage的最快方法？

Question

1. What is the fastest way to read Images from a File into a BufferedImage in Java/Grails?
2. What is the fastest way to write Images from a BufferedImage into a File in Java/Grails?

my variant (read):

byte [] imageByteArray = new File(basePath+imageSource).readBytes()
InputStream inStream = new ByteArrayInputStream(imageByteArray)
BufferedImage bufferedImage = ImageIO.read(inStream)

my variant (write):

BufferedImage bufferedImage = // some image
def fullPath = // image page + file name
byte [] currentImage

try{

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    ImageIO.write( bufferedImage, "jpg", baos );
    baos.flush();
    currentImage = baos.toByteArray();
    baos.close();

    }catch(IOException e){
        System.out.println(e.getMessage());
    }       
   }    


def newFile = new FileOutputStream(fullPath)
newFile.write(currentImage)
newFile.close()

Answer 1

Your solution to read is basically reading the bytes twice, once from the file and once from the ByteArrayInputStream . Don't do that

With Java 7 to read

BufferedImage bufferedImage = ImageIO.read(Files.newInputStream(Paths.get(basePath + imageSource)));

With Java 7 to write

ImageIO.write(bufferedImage, "jpg", Files.newOutputStream(Paths.get(fullPath)));

The call to Files.newInputStream will return a ChannelInputStream which (AFAIK) is not buffered. You'll want to wrap it

new BufferedInputStream(Files.newInputStream(...));

So that there are less IO calls to disk, depending on how you use it.

Answer 2

I'm late to the party, but anyway...

Actually, using:

ImageIO.read(new File(basePath + imageSource));

and

ImageIO.write(bufferedImage, "jpeg", new File(fullPath));

...might prove faster (try it, using a profiler, to make sure).

This is because these variants use RandomAccessFile -backed ImageInputStream / ImageOutputStream implementations behind the scenes, while the InputStream / OutputStream -based versions will by default use a disk-backed seekable stream implementation. The disk-backing involves writing the entire contents of the stream to a temporary file and possibly reading back from it (this is because image I/O often benefits from non-linear data access).

If you want to avoid extra I/O with the stream based versions, at the cost of using more memory, it is possible to call the ambiguously named ImageIO.setUseCache(false) , to disable disk caching of the seekable input streams. This is obviously not a good idea if you are dealing with very large images.

Answer 3

You are almost good for writing. Just don't use the intermediate ByteArrayOutputStream. It is a giant bottleneck in your code. Instead wrap the FileOutputStream in a BufferedOutputStream and do the same.

Same goes indeed for your reading. Remove the Itermediate ByteArrayInputStream.