converting Image to byte[]

* 파일 객체 생성

//// Read from a file

//File file = new File("img/strawberry.jpg");

//image = ImageIO.read(file);

//// Read from an input stream

//InputStream is = new BufferedInputStream(new FileInputStream("image.gif"));

//image = ImageIO.read(is);

// Read from a URL

//URL url = new URL("http://t2.gstatic.com/images?q=tbn:QWLWF6U_RKh34M:http://www.townofeb.com/IMAGES/soccer1.gif");

//image = ImageIO.read(url);

* 방법 1

        public byte[] convertByteArray(File file) throws Exception {

BufferedImage img = ImageIO.read(file);

ByteArrayOutputStream baos = new ByteArrayOutputStream((int) file.length());

    //    ImageIO 포맷가능한 파일들 알아보기

// String[] names = ImageIO.getWriterFormatNames();

// for ( String name: names )

// {

// System.out.println( name );

// }

String imgFormat = determineImageFormat(convertByteArray(file));

log.info(imgFormat);

// ImageIO.write(img,"png",baos);

ImageIO.write(img, imgFormat, baos);

baos.flush();

byte[] result = baos.toByteArray();

baos.close();

return result;

}

        private String determineImageFormat(byte[] imageBytes) throws IOException {

final ByteArrayInputStream bStream = new ByteArrayInputStream(imageBytes);

final ImageInputStream imgStream = ImageIO.createImageInputStream(bStream);

final Iterator<ImageReader> iter = ImageIO.getImageReaders(imgStream);

final ImageReader imgReader = iter.next();

return imgReader.getFormatName();

}

* 방법 2

public byte[] convertBytes(File file) throws Exception {

InputStream is = new FileInputStream(file);

long fileLength = file.length();

if (fileLength > Integer.MAX_VALUE) { // Integer.MAX_VALUE:2147483647

// File is too large

}

byte[] bytes = new byte[(int) fileLength];

int offset = 0;

int numRead = 0;

while (offset < bytes.length && (numRead = is.read(bytes, offset, bytes.length - offset)) >= 0) {

offset += numRead;

}

if (offset < bytes.length) {

throw new IOException("Could not completely read file " + file.getName());

}

is.close();

return bytes;

}