Compruebe el ancho y la altura de la imagen antes de cargarla con Javascript

Estoy de acuerdo. Una vez que se carga en algún lugar al que el navegador del usuario puede acceder, es bastante fácil obtener el tamaño. Como necesita esperar a que la imagen se cargue, querrá engancharse al evento onload para 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";

En mi opinión, la respuesta perfecta que debe requerir es

 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;
                        };

                    }

Función 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.");
            }

        }

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;
        }
    }