How to use JS to rotate the preview of IOS photo taken by 90 degrees

This time I will show you how to use JS to rotate the preview of the IOS photo taken by 90 degrees, and how to use JS to process the preview of the IOS photo taken 90 degrees by rotating it 90 degrees. , let’s take a look. To solve this problem, you need to introduce a third-party JS library: exif.js Download address:

github.com/exif-js/exif-js Through exif.js we can obtain the meta information of the image , which includes the direction in which the photo was taken. The photo direction

given by exif.js is used in IOS to obtain the direction of the photographed picture through exif.js. The returned value is 6, which is the case of the leftmost F in the above picture. This is where our bug lies. Therefore, we perform corresponding processing by judging the value of the direction. If the value is 6, we perform rotation correction on the image. The specific code is as follows:

//获取图片方向
function getPhotoOrientation(img) {
   var orient;
   EXIF.getData(img, function () {
      orient = EXIF.getTag(this, 'Orientation');
   });
   return orient;
}

Next, we will modify the compression function in the previous article as follows:

//图片压缩
function compress(img, width, height, ratio) {
   var canvas, ctx, img64, orient;
    
   //获取图片方向
   orient = getPhotoOrientation(img);
   canvas = document.createElement('canvas');
   canvas.width = width;
   canvas.height = height;
   ctx = canvas.getContext("2d");
   //如果图片方向等于6 ，则旋转矫正，反之则不做处理
   if (orient == 6) {
      ctx.save();
      ctx.translate(width / 2, height / 2);
      ctx.rotate(90 * Math.PI / 180);
      ctx.drawImage(img, 0 - height / 2, 0 - width / 2, height, width);
      ctx.restore();
   } else {
      ctx.drawImage(img, 0, 0, width, height);
   }
   img64 = canvas.toDataURL("image/jpeg", ratio);
   return img64;
}

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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