Check image width and height before upload with Ja

问题:

I have a JPS with a form in which a user can put an image:

<div class=\"photo\">
    <div>Photo (max 240x240 and 100 kb):</div>
    <input type=\"file\" name=\"photo\" id=\"photoInput\" onchange=\"checkPhoto(this)\"/>
</div>

I have written this js:

function checkPhoto(target) {
    if(target.files[0].type.indexOf(\"image\") == -1) {
        document.getElementById(\"photoLabel\").innerHTML = \"File not supported\";
        return false;
    }
    if(target.files[0].size > 102400) {
        document.getElementById(\"photoLabel\").innerHTML = \"Image too big (max 100kb)\";
        return false;
    }
    document.getElementById(\"photoLabel\").innerHTML = \"\";
    return true;
}

which works fine to check file type and size. Now I want to check image width and height but I cannot do it.
I have tried with target.files[0].width but I get undefined. With other ways I get 0.
Any suggestions?

回答1:

The file is just a file, you need to create an image like so:

var _URL = window.URL || window.webkitURL;
$(\"#file\").change(function (e) {
    var file, img;
    if ((file = this.files[0])) {
        img = new Image();
        img.onload = function () {
            alert(this.width + \" \" + this.height);
        };
        img.src = _URL.createObjectURL(file);
    }
});

Demo: http://jsfiddle.net/4N6D9/1/

I take it you realize this is only supported in a few browsers. Mostly firefox and chrome, could be opera as well by now.

回答2:

I agree. Once it is uploaded to somewhere the user\'s browser can access then it is pretty easy to get the size. As you need to wait for the image to load you\'ll want to hook into the onload event for img.

var width, height;

var img = document.createElement(\"img\");
img.onload = function() {
    // `naturalWidth`/`naturalHeight` aren\'t supported on <IE9. Fallback to normal width/height
    // The natural size is the actual image size regardless of rendering.
    // The \'normal\' width/height are for the **rendered** size.

    width  = img.naturalWidth  || img.width;
    height = img.naturalHeight || img.height; 

    // Do something with the width and height
}

// Setting the source makes it start downloading and eventually call `onload`
img.src = \"http://your.website.com/userUploadedImage.jpg\";

回答3:

In my view the perfect answer you must required is

 var reader = new FileReader();
    //Read the contents of Image File.
    reader.readAsDataURL(fileUpload.files[0]);
    reader.onload = function (e) {
    //Initiate the JavaScript Image object.
    var image = new Image();

    //Set the Base64 string return from FileReader as source.
                       image.src = e.target.result;

                        //Validate the File Height and Width.
                        image.onload = function () {
                            var height = this.height;
                            var width = this.width;
                            if (height > 100 || width > 100) {
                                alert(\"Height and Width must not exceed 100px.\");
                                return false;
                            }
                            alert(\"Uploaded image has valid Height and Width.\");
                            return true;
                        };

                    }

回答4:

function validateimg(ctrl) {

        var fileUpload = $(\"#txtPostImg\")[0];


        var regex = new RegExp(\"([a-zA-Z0-9\\s_\\\\.\\-:])+(.jpg|.png|.gif)$\");
        if (regex.test(fileUpload.value.toLowerCase())) {

            if (typeof (fileUpload.files) != \"undefined\") {

                var reader = new FileReader();

                reader.readAsDataURL(fileUpload.files[0]);
                reader.onload = function (e) {

                    var image = new Image();

                    image.src = e.target.result;
                    image.onload = function () {

                        var height = this.height;
                        var width = this.width;
                        console.log(this);
                        if ((height >= 1024 || height <= 1100) && (width >= 750 || width <= 800)) {
                            alert(\"Height and Width must not exceed 1100*800.\");
                            return false;
                        }
                        alert(\"Uploaded image has valid Height and Width.\");
                        return true;
                    };
                }
            } else {
                alert(\"This browser does not support HTML5.\");
                return false;
            }
        } else {
            alert(\"Please select a valid Image file.\");
            return false;
        }
    }

回答5:

function uploadfile(ctrl) {
    var validate = validateimg(ctrl);

    if (validate) {
        if (window.FormData !== undefined) {
            ShowLoading();
            var fileUpload = $(ctrl).get(0);
            var files = fileUpload.files;


            var fileData = new FormData();


            for (var i = 0; i < files.length; i++) {
                fileData.append(files[i].name, files[i]);
            }


            fileData.append(\'username\', \'Wishes\');

            $.ajax({
                url: \'UploadWishesFiles\',
                type: \"POST\",
                contentType: false,
                processData: false,
                data: fileData,
                success: function(result) {
                    var id = $(ctrl).attr(\'id\');
                    $(\'#\' + id.replace(\'txt\', \'hdn\')).val(result);

                    $(\'#imgPictureEn\').attr(\'src\', \'../Data/Wishes/\' + result).show();

                    HideLoading();
                },
                error: function(err) {
                    alert(err.statusText);
                    HideLoading();
                }
            });
        } else {
            alert(\"FormData is not supported.\");
        }

    }