Java（J2ME）将Image转换为byte []，然后返回Image [英] Java (J2ME) Convert Image to byte[], then back to Image
问题描述
我正在尝试将Image对象转换为字节数组，然后再转换为Image（这样我就可以将图像存储在Apache Derby数据库的blob对象中）。
I'm trying to convert an Image object to a byte array then back to an Image (so that I can store the image in a blob object in an Apache Derby Database).
我可以将Image转换为字节数组（下面的代码），但我无法将字节转换回图像。作为一个更复杂的我正在使用J2ME，所以我不能使用javax.image。*。
你能帮忙吗？
I can convert an Image to a byte array (code below) but I cann't convert the bytes back to an image. As a further complication I'm using J2ME, so I can't use javax.image.*. Can you help?
谢谢
package six.util;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.awt.image.ImageObserver;
import java.awt.Component;
import java.awt.MediaTracker;
import java.awt.Graphics;
import java.awt.image.DataBufferByte;
import java.awt.image.WritableRaster;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.image.PixelGrabber;
import java.util.ArrayList;
public class ImageConverter extends Component
{
private MediaTracker mediaTracker;
private Image image;
private ImageConverter(Image image)
{
super();
this.mediaTracker = new MediaTracker(this);
this.mediaTracker.addImage(image, 0);
this.image = image;
}
private BufferedImage convert()
{
/*
* Have to wait for image to load.
*/
try
{
this.mediaTracker.waitForID(0);
}catch(InterruptedException e)
{
}
System.out.println("-1");
GraphicsConfiguration graphicsConfig = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
BufferedImage bimage = graphicsConfig.createCompatibleImage(this.image.getWidth(null),this.image.getHeight(null));
System.out.println("-2");
Graphics g = bimage.getGraphics();
g.drawImage(image, 0, 0, null);
return bimage;
}
private static byte[] convertIntToByteArray(int integer)
{
byte[] bytes = new byte[4];
bytes[0] =(byte)( integer >> 24 );
bytes[1] =(byte)( (integer << 8) >> 24 );
bytes[2] =(byte)( (integer << 16) >> 24 );
bytes[3] =(byte)( (integer << 24) >> 24 );
return bytes;
}
private static int convertByteArrayToInt(byte[] bytes)
{
return (bytes[0] << 32) | (bytes[1] << 24) | (bytes[2] << 16) | (bytes[3] << 8) | bytes[4];
}
private static byte[] convertIntArrayToByteArray(int[] integers)
{
byte[] bytes = new byte[integers.length*4];
for (int index = 0; index < integers.length; index++)
{
byte[] integerBytes = convertIntToByteArray(integers[index]);
bytes[index*4] = integerBytes[0];
bytes[1 + (index*4)] = integerBytes[1];
bytes[2 + (index*4)] = integerBytes[2];
bytes[3 + (index*4)] = integerBytes[3];
}
return bytes;
}
private static int[] convertByteArrayToIntArray(byte[] bytes)
{
ArrayList integers = new ArrayList();
for (int index = 0; index < bytes.length; index += 4)
{
byte[] fourBytes = new byte[4];
fourBytes[0] = bytes[index];
fourBytes[1] = bytes[index+1];
fourBytes[2] = bytes[index+2];
fourBytes[3] = bytes[index+3];
int integer = convertByteArrayToInt(fourBytes);
integers.add(new Integer(integer));
}
int[] ints = new int[bytes.length/4];
for (int index = 0; index < integers.size() ; index++)
{
ints[index] = ((Integer)integers.get(index)).intValue();
}
return ints;
}
public static byte[] convertToBytes(Image image)
{
System.out.println("A");
ImageConverter converter = new ImageConverter(image);
System.out.println("B");
BufferedImage bufferedImage = converter.convert();
System.out.println("C");
PixelGrabber pixelGrabber = new PixelGrabber(image,0,0,bufferedImage.getWidth(),bufferedImage.getHeight(),true);
System.out.println("D");
try
{
if(pixelGrabber.grabPixels())
{
Object pixels = pixelGrabber.getPixels();
if (pixels instanceof byte[])
{
return (byte[])pixels;
}
return convertIntArrayToByteArray((int[])pixels);
}
}catch(InterruptedException e)
{
}
return null;
}
}
推荐答案
要重新创建图像，可以在Image类中使用createRGBImage方法（ http://java.sun.com/javame/reference/apis/jsr118/ ）但请注意，您对图像中的每个像素使用4个字节。宽度为200 x 200像素的图像总共将有40000像素，这将占用移动设备中160KB的内存。
To recreate the image you can use the method createRGBImage in the Image class (http://java.sun.com/javame/reference/apis/jsr118/), but be aware that you're using 4 bytes for each pixel in the image. A image with 200 x 200 pixels of width will have 40000 pixels in total, which will occupy 160KB of memory in the mobile device.
我在J2ME中使用过图像之前，但只将图像从服务器发送到客户端。在这种情况下，您可以更改服务器上的图像分辨率（您有代码和原始功率），将其编码为JPEG，然后将其发送到客户端。 Image.createImage（...）方法可以创建运行应用程序的J2ME引擎支持的任何编码格式的图像。我相信JPEG将永远被接受。
I've worked with images in J2ME before, but only sending the images from the server to the client. In that case, you can change the resolution of the image on the server (where you have the code and the raw power to do that), encode it as JPEG and then send it to the client. The method Image.createImage(...) can create an image in any encoded format supported by the J2ME engine that is running the application. I believe that JPEG will always be accepted.
即使您需要这些图像供将来使用，您也可以将服务器返回的byte []缓冲区保存在Record Store中然后使用它。
Even if you need those images for future use, you can save the byte[] buffer returned by the server in a Record Store and then use it.
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