今天遇到個問題,通過iphone上傳圖片到伺服器,後臺人員拿到的圖片是橫著的.
先說下原因,在網上查過很多資料,最終確定的原定是
用相機拍攝出來的照片含有EXIF資訊,UIImage的imageOrientation屬性指的就是EXIF中的orientation資訊.如果我們忽略orientation資訊,而直接對照片進行畫素處理或者drawInRect等操作,得到的結果是翻轉或者旋轉90之後的樣子。這是因為我們執行畫素處理或者drawInRect等操作之後，imageOrientaion資訊被刪除了,imageOrientaion被重設為0，造成照片內容和imageOrientaion不匹配.所以,在對照片進行處理之前,先將照片旋轉到正確的方向,並且返回的imageOrientaion為0。
下面是程式碼

/**
         * 旋轉圖片
         */
        Metadata metadata = JpegMetadataReader.readMetadata(new File(圖片路徑));
        Directory directory = metadata.getFirstDirectoryOfType(ExifDirectoryBase.class);
        int orientation = 0;
        if (directory != null && directory.containsTag(ExifDirectoryBase.TAG
 
_ORIENTATION)) { // Exif資訊中有儲存方向,把資訊複製到縮圖
            orientation = directory.getInt(ExifDirectoryBase.TAG_ORIENTATION); // 原圖片的方向資訊
            System.err.println("orientation:" + orientation);
        }

        if (orientation == 1) {
            System.out.println("rotate 90");
            BufferedImage src = ImageIO.read
 
(new File(poetry.getPicurl()));
            BufferedImage des = RotateImage.Rotate(src, 0);
            ImageIO.write(des, "jpg", new File(poetry.getPicurl()));
        } else if (6 == orientation) {
            // 6旋轉90
            System.out.println("rotate 90");
            BufferedImage src = ImageIO.read(new File(poetry.getPicurl()));
            BufferedImage des = RotateImage.Rotate(src, 90);
            ImageIO.write(des, "jpg", new File(poetry.getPicurl()));
        } else if (3 == orientation) {
            // 3旋轉180
            System.out.println("rotate 180");
            BufferedImage src = ImageIO.read(new File(poetry.getPicurl()));
            BufferedImage des = RotateImage.Rotate(src, 180);
            ImageIO.write(des, "jpg", new File(poetry.getPicurl()));
        } else if (8 == orientation) {
            // 8旋轉90
            System.out.println("rotate 90");
            BufferedImage src = ImageIO.read(new File(poetry.getPicurl()));
            BufferedImage des = RotateImage.Rotate(src, 270);
            ImageIO.write(des, "jpg", new File(poetry.getPicurl()));
        }

下面是幫助類

public class RotateImage {
     public static BufferedImage Rotate(Image src, int angel) {  
         int src_width = src.getWidth(null);  
         int src_height = src.getHeight(null);  
         // calculate the new image size  
         Rectangle rect_des = CalcRotatedSize(new Rectangle(new Dimension(  
                 src_width, src_height)), angel);  

         BufferedImage res = null;  
         res = new BufferedImage(rect_des.width, rect_des.height,  
                 BufferedImage.TYPE_INT_RGB);  
         Graphics2D g2 = res.createGraphics();  
         // transform  
         g2.translate((rect_des.width - src_width) / 2,  
                 (rect_des.height - src_height) / 2);  
         g2.rotate(Math.toRadians(angel), src_width / 2, src_height / 2);  

         g2.drawImage(src, null, null);  


         return res;  
     }  



     public static Rectangle CalcRotatedSize(Rectangle src, int angel) {  
         // if angel is greater than 90 degree, we need to do some conversion  
         if (angel >= 90) {  
             if(angel / 90 % 2 == 1){  
                 int temp = src.height;  
                 src.height = src.width;  
                 src.width = temp;  
             }  
             angel = angel % 90;  
         }  

         double r = Math.sqrt(src.height * src.height + src.width * src.width) / 2;  
         double len = 2 * Math.sin(Math.toRadians(angel) / 2) * r;  
         double angel_alpha = (Math.PI - Math.toRadians(angel)) / 2;  
         double angel_dalta_width = Math.atan((double) src.height / src.width);  
         double angel_dalta_height = Math.atan((double) src.width / src.height);  

         int len_dalta_width = (int) (len * Math.cos(Math.PI - angel_alpha  
                 - angel_dalta_width));  
         int len_dalta_height = (int) (len * Math.cos(Math.PI - angel_alpha  
                 - angel_dalta_height));  
         int des_width = src.width + len_dalta_width * 2;  
         int des_height = src.height + len_dalta_height * 2;  


         return new Rectangle(new Dimension(des_width, des_height));  
     }