Accessing JPEG EXIF rotation data in JavaScript on the client side_问答_开发者

I'd like to rotate photos based on their original rotation, as set by the camera in JPEG EXIF image data. The trick is that all this should happen in the browser, using JavaScript and <canvas>.

How could JavaScript access JPEG, a local file API object, local <img> or remote <img>, EXIF data to read the rotation information?

开发者_运维技巧

Server-side answers are not OK; I am looking for a client-side solution.

If you only want the orientation tag and nothing else and don't like to include another huge javascript library I wrote a little code that extracts the orientation tag as fast as possible (It uses DataView and readAsArrayBuffer which are available in IE10+, but you can write your own data reader for older browsers):

function getOrientation(file, callback) {
    var reader = new FileReader();
    reader.onload = function(e) {

        var view = new DataView(e.target.result);
        if (view.getUint16(0, false) != 0xFFD8)
        {
            return callback(-2);
        }
        var length = view.byteLength, offset = 2;
        while (offset < length) 
        {
            if (view.getUint16(offset+2, false) <= 8) return callback(-1);
            var marker = view.getUint16(offset, false);
            offset += 2;
            if (marker == 0xFFE1) 
            {
                if (view.getUint32(offset += 2, false) != 0x45786966) 
                {
                    return callback(-1);
                }

                var little = view.getUint16(offset += 6, false) == 0x4949;
                offset += view.getUint32(offset + 4, little);
                var tags = view.getUint16(offset, little);
                offset += 2;
                for (var i = 0; i < tags; i++)
                {
                    if (view.getUint16(offset + (i * 12), little) == 0x0112)
                    {
                        return callback(view.getUint16(offset + (i * 12) + 8, little));
                    }
                }
            }
            else if ((marker & 0xFF00) != 0xFF00)
            {
                break;
            }
            else
            { 
                offset += view.getUint16(offset, false);
            }
        }
        return callback(-1);
    };
    reader.readAsArrayBuffer(file);
}

// usage:
var input = document.getElementById('input');
input.onchange = function(e) {
    getOrientation(input.files[0], function(orientation) {
        alert('orientation: ' + orientation);
    });
}

<input id='input' type='file' />

values:

-2: not jpeg
-1: not defined

Accessing JPEG EXIF rotation data in JavaScript on the client side

For those using Typescript, you can use the following code:

export const getOrientation = (file: File, callback: Function) => {
  var reader = new FileReader();

  reader.onload = (event: ProgressEvent) => {

    if (! event.target) {
      return;
    }

    const file = event.target as FileReader;
    const view = new DataView(file.result as ArrayBuffer);

    if (view.getUint16(0, false) != 0xFFD8) {
        return callback(-2);
    }

    const length = view.byteLength
    let offset = 2;

    while (offset < length)
    {
        if (view.getUint16(offset+2, false) <= 8) return callback(-1);
        let marker = view.getUint16(offset, false);
        offset += 2;

        if (marker == 0xFFE1) {
          if (view.getUint32(offset += 2, false) != 0x45786966) {
            return callback(-1);
          }

          let little = view.getUint16(offset += 6, false) == 0x4949;
          offset += view.getUint32(offset + 4, little);
          let tags = view.getUint16(offset, little);
          offset += 2;
          for (let i = 0; i < tags; i++) {
            if (view.getUint16(offset + (i * 12), little) == 0x0112) {
              return callback(view.getUint16(offset + (i * 12) + 8, little));
            }
          }
        } else if ((marker & 0xFF00) != 0xFF00) {
            break;
        }
        else {
            offset += view.getUint16(offset, false);
        }
    }
    return callback(-1);
  };

  reader.readAsArrayBuffer(file);
}

You can use the exif-js library in combination with the HTML5 File API: http://jsfiddle.net/xQnMd/1/.

$("input").change(function() {
    var file = this.files[0];  // file
        fr   = new FileReader; // to read file contents

    fr.onloadend = function() {
        // get EXIF data
        var exif = EXIF.readFromBinaryFile(new BinaryFile(this.result));

        // alert a value
        alert(exif.Make);
    };

    fr.readAsBinaryString(file); // read the file
});

Firefox 26 supports image-orientation: from-image: images are displayed portrait or landscape, depending on EXIF data. (See sethfowler.org/blog/2013/09/13/new-in-firefox-26-css-image-orientation.)

There is also a bug to implement this in Chrome.

Beware that this property is only supported by Firefox and is likely to be deprecated.

https://github.com/blueimp/JavaScript-Load-Image is a modern javascript library that can not only extract the exif orientation flag - it can also correctly mirror/rotate JPEG images on the client side.

I just solved the same problem with this library: JS Client-Side Exif Orientation: Rotate and Mirror JPEG Images

I upload expansion code to show photo by android camera on html as normal on some img tag with right rotaion, especially for img tag whose width is wider than height. I know this code is ugly but you don't need to install any other packages. (I used above code to obtain exif rotation value, Thank you.)

function getOrientation(file, callback) {
  var reader = new FileReader();
  reader.onload = function(e) {

    var view = new DataView(e.target.result);
    if (view.getUint16(0, false) != 0xFFD8) return callback(-2);
    var length = view.byteLength, offset = 2;
    while (offset < length) {
      var marker = view.getUint16(offset, false);
      offset += 2;
      if (marker == 0xFFE1) {
        if (view.getUint32(offset += 2, false) != 0x45786966) return callback(-1);
        var little = view.getUint16(offset += 6, false) == 0x4949;
        offset += view.getUint32(offset + 4, little);
        var tags = view.getUint16(offset, little);
        offset += 2;
        for (var i = 0; i < tags; i++)
          if (view.getUint16(offset + (i * 12), little) == 0x0112)
            return callback(view.getUint16(offset + (i * 12) + 8, little));
      }
      else if ((marker & 0xFF00) != 0xFF00) break;
      else offset += view.getUint16(offset, false);
    }
    return callback(-1);
  };
  reader.readAsArrayBuffer(file);
}

var isChanged = false;
function rotate(elem, orientation) {
    if (isIPhone()) return;

    var degree = 0;
    switch (orientation) {
        case 1:
            degree = 0;
            break;
        case 2:
            degree = 0;
            break;
        case 3:
            degree = 180;
            break;
        case 4:
            degree = 180;
            break;
        case 5:
            degree = 90;
            break;
        case 6:
            degree = 90;
            break;
        case 7:
            degree = 270;
            break;
        case 8:
            degree = 270;
            break;
    }
    $(elem).css('transform', 'rotate('+ degree +'deg)')
    if(degree == 90 || degree == 270) {
        if (!isChanged) {
            changeWidthAndHeight(elem)
            isChanged = true
        }
    } else if ($(elem).css('height') > $(elem).css('width')) {
        if (!isChanged) {
            changeWidthAndHeightWithOutMargin(elem)
            isChanged = true
        } else if(degree == 180 || degree == 0) {
            changeWidthAndHeightWithOutMargin(elem)
            if (!isChanged)
                isChanged = true
            else
                isChanged = false
        }
    }
}


function changeWidthAndHeight(elem){
    var e = $(elem)
    var width = e.css('width')
    var height = e.css('height')
    e.css('width', height)
    e.css('height', width)
    e.css('margin-top', ((getPxInt(height) - getPxInt(width))/2).toString() + 'px')
    e.css('margin-left', ((getPxInt(width) - getPxInt(height))/2).toString() + 'px')
}

function changeWidthAndHeightWithOutMargin(elem){
    var e = $(elem)
    var width = e.css('width')
    var height = e.css('height')
    e.css('width', height)
    e.css('height', width)
    e.css('margin-top', '0')
    e.css('margin-left', '0')
}

function getPxInt(pxValue) {
    return parseInt(pxValue.trim("px"))
}

function isIPhone(){
    return (
        (navigator.platform.indexOf("iPhone") != -1) ||
        (navigator.platform.indexOf("iPod") != -1)
    );
}

and then use such as

$("#banner-img").change(function () {
    var reader = new FileReader();
    getOrientation(this.files[0], function(orientation) {
        rotate($('#banner-img-preview'), orientation, 1)
    });

    reader.onload = function (e) {
        $('#banner-img-preview').attr('src', e.target.result)
        $('#banner-img-preview').css('display', 'inherit')

    };

    // read the image file as a data URL.
    reader.readAsDataURL(this.files[0]);

});

If you want it cross-browser, your best bet is to do it on the server. You could have an API that takes a file URL and returns you the EXIF data; PHP has a module for that.

This could be done using Ajax so it would be seamless to the user. If you don't care about cross-browser compatibility, and can rely on HTML5 file functionality, look into the library JsJPEGmeta that will allow you to get that data in native JavaScript.

Improving / Adding more functionality to Ali's answer from earlier, I created a util method in Typescript that suited my needs for this issue. This version returns rotation in degrees that you might also need for your project.

ImageUtils.ts

/**
 * Based on StackOverflow answer: https://stackoverflow.com/a/32490603
 *
 * @param imageFile The image file to inspect
 * @param onRotationFound callback when the rotation is discovered. Will return 0 if if it fails, otherwise 0, 90, 180, or 270
 */
export function getOrientation(imageFile: File, onRotationFound: (rotationInDegrees: number) => void) {
  const reader = new FileReader();
  reader.onload = (event: ProgressEvent) => {
    if (!event.target) {
      return;
    }

    const innerFile = event.target as FileReader;
    const view = new DataView(innerFile.result as ArrayBuffer);

    if (view.getUint16(0, false) !== 0xffd8) {
      return onRotationFound(convertRotationToDegrees(-2));
    }

    const length = view.byteLength;
    let offset = 2;

    while (offset < length) {
      if (view.getUint16(offset + 2, false) <= 8) {
        return onRotationFound(convertRotationToDegrees(-1));
      }
      const marker = view.getUint16(offset, false);
      offset += 2;

      if (marker === 0xffe1) {
        if (view.getUint32((offset += 2), false) !== 0x45786966) {
          return onRotationFound(convertRotationToDegrees(-1));
        }

        const little = view.getUint16((offset += 6), false) === 0x4949;
        offset += view.getUint32(offset + 4, little);
        const tags = view.getUint16(offset, little);
        offset += 2;
        for (let i = 0; i < tags; i++) {
          if (view.getUint16(offset + i * 12, little) === 0x0112) {
            return onRotationFound(convertRotationToDegrees(view.getUint16(offset + i * 12 + 8, little)));
          }
        }
        // tslint:disable-next-line:no-bitwise
      } else if ((marker & 0xff00) !== 0xff00) {
        break;
      } else {
        offset += view.getUint16(offset, false);
      }
    }
    return onRotationFound(convertRotationToDegrees(-1));
  };
  reader.readAsArrayBuffer(imageFile);
}

/**
 * Based off snippet here: https://github.com/mosch/react-avatar-editor/issues/123#issuecomment-354896008
 * @param rotation converts the int into a degrees rotation.
 */
function convertRotationToDegrees(rotation: number): number {
  let rotationInDegrees = 0;
  switch (rotation) {
    case 8:
      rotationInDegrees = 270;
      break;
    case 6:
      rotationInDegrees = 90;
      break;
    case 3:
      rotationInDegrees = 180;
      break;
    default:
      rotationInDegrees = 0;
  }
  return rotationInDegrees;
}

Usage:

import { getOrientation } from './ImageUtils';
...
onDrop = (pics: any) => {
  getOrientation(pics[0], rotationInDegrees => {
    this.setState({ image: pics[0], rotate: rotationInDegrees });
  });
};

Check out a module I've written (you can use it in browser) which converts exif orientation to CSS transform: https://github.com/Sobesednik/exif2css

There is also this node program to generate JPEG fixtures with all orientations: https://github.com/Sobesednik/generate-exif-fixtures