ImageItem.java

/**
 *
 */
package com.keju.maomao.internet;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * 临时存储上传图片的内容，格式，文件信息等
 * 
 * @author 
 * 
 */
public class ImageItem {
	  /**
     * detect bytes's image type by file
     * @param fileItem
     * @return
     * @see #getImageType(byte[])
     * 
     */
	private byte[] content;
	private String name;
	private String ImageType;
	
	public ImageItem(String name,byte[] content) throws Exception{
		String imgtype=getImageType(content);
		
	    if(imgtype!=null&&(imgtype.equalsIgnoreCase("image/gif")||imgtype.equalsIgnoreCase("image/png")
	            ||imgtype.equalsIgnoreCase("image/jpeg"))){
	    	this.content=content;
	    	this.name=name;
	    	this.ImageType=imgtype;
	    }else{
	    	throw new IllegalStateException(
            "Unsupported image type, Only Suport JPG ,GIF,PNG!");
	    }
	}
//	public ImageItem(byte[] content) throws Exception{
//		this(SystemConstants.UPLOAD_MODE,content);
//	}
	
	public byte[] getContent() {
		return content;
	}
	public String getName() {
		return name;
	}
	public String getImageType() {
		return ImageType;
	}
    public static String getImageType(File file){
        if(file == null||!file.exists()){
            return null;
        }
        InputStream in = null;
        try {
            in = new FileInputStream(file);
            String type = getImageType(in);
            return type;
        } catch (IOException e) {
            return null;
        }finally{
            try{
                if(in != null){
                    in.close();
                }
            }catch(IOException e){
            }
        }
    }
    
    /**
     * detect bytes's image type by inputstream
     * @param in
     * @return
     * @see #getImageType(byte[])
     */
    public static String getImageType(InputStream in) {
        if(in == null){
            return null;
        }
        try{
            byte[] bytes = new byte[8];
            in.read(bytes);
            return getImageType(bytes);
        }catch(IOException e){
            return null;
        }
    }

    /**
     * detect bytes's image type
     * @param bytes 2~8 byte at beginning of the image file  
     * @return image mimetype or null if the file is not image
     */
    public static String getImageType(byte[] bytes) {
        if (isJPEG(bytes)) {
            return "image/jpeg";
        }
        if (isGIF(bytes)) {
            return "image/gif";
        }
        if (isPNG(bytes)) {
            return "image/png";
        }
        if (isBMP(bytes)) {
            return "application/x-bmp";
        }
        return null;
    }

    private static boolean isJPEG(byte[] b) {
        if (b.length < 2) {
            return false;
        }
        return (b[0] == (byte)0xFF) && (b[1] == (byte)0xD8);
    }

    private static boolean isGIF(byte[] b) {
        if (b.length < 6) {
            return false;
        }
        return b[0] == 'G' && b[1] == 'I' && b[2] == 'F' && b[3] == '8'
                && (b[4] == '7' || b[4] == '9') && b[5] == 'a';
    }

    private static boolean isPNG(byte[] b) {
        if (b.length < 8) {
            return false;
        }
        return (b[0] == (byte) 137 && b[1] == (byte) 80 && b[2] == (byte) 78
                && b[3] == (byte) 71 && b[4] == (byte) 13 && b[5] == (byte) 10
                && b[6] == (byte) 26 && b[7] == (byte) 10);
    }

    private static boolean isBMP(byte[] b) {
        if (b.length < 2) {
            return false;
        }
        return (b[0] == 0x42) && (b[1] == 0x4d);
    }
}