上传图片时控制图片的宽度和高度

Question

Straight to point. I want to set the limit of the width and height of the image when user upload an image using plupload.

Letsay: if width: 1000px height: 1000px else you must upload image with at least width:1000px and height:1000px

// $(".form").validator();
$(function() {
    if($("#uploader").length > 0) {
        var uploader = new plupload.Uploader({
            runtimes : 'html5,flash,silverlight',
            browse_button : 'pickfile',
            container : 'uploader',
            max_file_size : '10mb',
            url : 'design.php?do=upload&ajax=1',
            multiple_queues: false,
            file_data_name: 'design',
            flash_swf_url : www + '/js/plupload.flash.swf',
            silverlight_xap_url : www + '/js/plupload.silverlight.xap',
            filters : [
                {title : "Image files", extensions : "jpg,gif,png,jpeg,bmp"}
            ]

        });

        $('#uploadfiles').click(function(e) {
            if($("#uploader select[name=category]").val() == "") {
                $("#uploader select[name=category]").next('.error-required').show();
                return false;
            }

            uploader.start();
            e.preventDefault();
        });

        uploader.init();

So, is this possible?

Answer 1

You can easily write a filter for plupload.

Here is filter for min required width. Add bellow code to your script. (Just copy)

plupload.addFileFilter('min_width', function(maxwidth, file, cb) {
    var self = this, img = new o.Image();

    function finalize(result) {
        // cleanup
        img.destroy();
        img = null;

       // if rule has been violated in one way or another, trigger an error
        if (!result) {
            self.trigger('Error', {
                code : plupload.IMAGE_DIMENSIONS_ERROR,
                message : "Image width should be more than " + maxwidth  + " pixels.",
                file : file
            });
     }
        cb(result);
    }
    img.onload = function() {
        // check if resolution cap is not exceeded
        finalize(img.width >= maxwidth);
    };
    img.onerror = function() {
        finalize(false);
    };
    img.load(file.getSource());
});

And add this filter to your upload script.

filters : {
            min_width: 700,
        },

Answer 2

Plupload doesn't support this itself ( although it has been requested ). There are probably a couple of reasons for this, firstly because you just can't get the image dimensions before upload in IE ( you can in some other browsers ) and secondly, whilst that would work for some browsers using the using the HTML4/5 methods, I am not sure that the Flash/Silverlight etc. methods would also be able to reliably determine dimensions.

If you were happy with limited browser, HTML4/5 methods only you should hook into the "FilesAdded" event eg

uploader.bind('FilesAdded', function(up, files) {
  //Get src of each file, create image, remove from file list if too big
});

Answer 3

I recently wanted to do the same thing, and was able to achieve it the way Thom was suggesting. He was correct on it's limitation though; if you want to add this, it will only work in modern browsers and not in the flash or silverlight runtimes. This is not a huge issue, as my non-html5 users will just get an error after upload, rather than before.

I initialized a total image count variable to keep track of the images placed on the page. Also a vairable to store photos we want to delete after we read them all.

var total_image_count = 0;
var files_to_remove = [];

Then I read the pending files with FileReader(), place them on the page, and get their width

init:{
        FilesAdded: function(up, files) {
           if (uploader.runtime == "html5"){
              files = jQuery("#"+uploader.id+"_html5")[0].files
              console.log(files);
              for (i in files){

                 //create image tag for the file we are uploading
                 jQuery("<img />").attr("id","image-"+total_image_count).appendTo("#upload-container");

                 reader_arr[total_image_count] = new FileReader();

                 //create listener to place the data in the newly created 
                 //image tag when FileReader fully loads image.
                 reader_arr[total_image_count].onload = function(total_image_count) {
                    return function(e){
                       var img = $("#image-"+total_image_count);
                       img.attr('src', e.target.result);
                       if ($(img)[0].naturalWidth < 1000){

                          files_to_remove.push(files[i]); //remove them after we finish reading in all the files
                          //This is where you would append an error to the DOM if you wanted.
                          console.log("Error. File must be at least 1000px");
                       }
                    }
                 }(total_image_count);

                 reader_arr[total_image_count].readAsDataURL(files[i]);

                 total_image_count++;
              }
              for (i in files_to_remove){
                 uploader.removeFile(files_to_remove[i]);
              }
           }
        }
     }

As a side note, I was wanting to show image thumbnails anyway, so this method works great for me. I have not figured out how to get an image's width without first appending it to the DOM.

Sources:

Thumbnail an image before upload: https://stackoverflow.com/a/4459419/686440

Accessing image's natural width: https://stackoverflow.com/a/1093414/686440

Answer 4

to access width and heigth without thumbnail an image you can do this:

uploader.bind('FilesAdded', function(up, files) {
    files = jQuery("#"+uploader.id+"_html5").get(0).files;
    jQuery.each(files, function(i, file) {
        var reader = new FileReader();
        reader.onload = (function(e) { 
            var image = new Image();
            image.src = e.target.result;

                image.onload = function() {
                    // access image size here using this.width and this.height
                }
            };

        });

        reader.readAsDataURL(file);
    }
}