Display image after file input selection with image resize - javascript

I have seen posts asking how to display an image selected via a file input control. When I try these solutions, they work, yet I have a further issue I am unable to discover an answer to on my own: When I select an image for the first time, the image will not display because no image width and height data is available (image data is available via the FileReader obj, yet not the image width and height). The second time the image is selected (or after a reload), the width and height become available. Why is this occurring and what can I do to fix it? thanks.
Here's some code I've been using - this is one of the FileReader functions. I started by using reader.onload, but then thought the image width and height were not available because it hadn't loaded fully yet. Therefore onloadend seemed a better choice. It doesn't work any better here, though:
reader.onloadend = function(e) {
var img = new Image();
img.src = e.target.result;// or reader.result - doesn't matter
// A function that does math to proportionally scale the image
var new_size = scaleImageSize(150, 150, img.width, img.height);
img.width = new_size[0];
img.height = new_size[1];
// And here I am trying both ways to display the image: the first
// in a div tag, the second straight into an img tag. I only want
// to use one of these - preferably the div tag. I have also tried
// drawing the image onto an HTML5 canvas. All to no avail.
document.getElementById("file_display_area").appendChild(img);
document.getElementById("img_file_display_area").src = img.src;
console.log(img.width + '|' + img.height + '||' + new_size[0] + '|' + new_size[1]);
}

Related

getting size of image from a link as dynamic content

I want to make an image previewer inside a page. I will have a "div" to include smaller images by setting the size of "img" by hand. Then clicked or hovered, the image will show on a bigger "div", as small as the image itself or as big as window view size near the mouse pointer. the code will have only image link and will get actual image size from there.
setting the size and position of previewer "div" is just a mathematical problem for me. but I can't seem to find how to get image size by the link. I tried only to get mostly undefined values if not errors.
Be careful while answering that most of the thought methods get the size from the "img" element itself if sizes are set, but returns null if not.
CAUTION: this is similar to How to get image size (height & width) using JavaScript? , but (a) accepted answer does not work for me. it gives either 0x0 or undefined. (b) suggested answer of Josh Stodola works only if image loaded with window. my link is dynamic.
this is also similar to Get width height of remote image from url. It works with alert function, but I cant get the size out of the said functions as I need them for calculations.
I updated my answer. It now triggers on a mouseover event and doesn't use an ID. Be sure to accept the answer if this is working for you.
function getMeta(imageSrc,callback) {
var img = new Image();
img.src = imageSrc;
img.onload = function() { callback(this.width, this.height); }
}
function hoverLink(imageSrc){
getMeta(
imageSrc,
function(width, height) {
document.getElementById("prev").innerHTML = width + 'px ' + height + 'px';
}
);
}
function hoverOff(){
document.getElementById("prev").innerHTML ='';
}
<a href="https://res.cloudinary.com/rss81/image/upload/gw.jpg"
onmouseover="hoverLink(this.href)"
onmouseout="hoverOff()">
Picture Link
</a>
<div id='prev'></div>
Thanks to #dcr, I got the problem over. He helped me with the code, and I have seen the problem that confused me.
Those answers to other posts mostly used "alert" function, which is not a good way to show how to get required value, in my case the size of an image.
Here in this code, it can clearly be seen that "getMeta" and "caller" functions are merely an interface to "setter". I can reference any required value from "callback" part and "setter" can then be expanded to the needs, in my case calculating the size and position of my previewer "div". The only difference with #dcr 's solution is getting the "setter" function out of "caller" function.
function getMeta(imageSrc,callback) {
var img = new Image();
img.src = imageSrc;
img.onload = function() { callback(this.width, this.height); }
}
function caller(imageSrc){
getMeta( imageSrc,setter);
}
function setter(width, height) {
document.getElementById("prev").innerHTML = width + 'px X ' + height + 'px';
}
Picture Link
<div id='prev'></div>

How to view an image file's dimension with javascript

I'm trying to assign variables that store the height and width of an image from the local "img" folder. I tried something along the lines of
myWidth = (("img/myImage.png").naturalWidth);
but as far as I can tell, that only works if the image is already present somewhere on the page. Is there a way to do this by getting Javascript to view the file's properties in the folder?
EDIT: I'm not doing anything too technical. I just have 600 or so small images that need to be in separate divs that are the same pixel width and height as the image, and each image is different. I'm trying to write a script to generate all the code for my css without having to type it all in manually.
You can use an Image element to get the dimensions. I have previously created a tool that fetches image dimensions via JavaScript for an SO question. You can see it in action here: https://codepen.io/NikxDa/pen/apegZa
Necessary part:
var img = new Image ();
// Handle onload (will contain data after file has loaded)
img.onload = function () {
alert ("The dimensions are: " + this.width + "x" + this.height);
};
// Load the file by fileUrl
img.src = <fileUrl>;
Hope it helps.

Get image dimensions after resizing

I have encountered a problem that other people had in this website before but none of the solutions helped me slightly.
I have a method that updates an image inside a div (read: user uploads a new image) where the image is resized to fit the set proportions (max-height and max-width are 45x45). I have to resize the div that holds the image to 2* it's dimensions such as the example below:
Original image is 180x180.
It is resized to 45x45. Div has to be 90x90.
Code is as follows:
function uploadThumbnail(id, xCoord, yCoord) {
var oFReader = new FileReader();
oFReader.readAsDataURL(document.getElementById("thumbnailLoader"+id).files[0]);
oFReader.onload = function(oFREvent) {
var mapThumbnail = updateMapThumbnail(oFREvent.target.result, id);
var mapContainer = document.getElementById("thumbnail"+id);
var informationContainer = document.getElementById("container"+id);
console.log(mapThumbnail.width);
mapContainer.removeChild(document.getElementById("mapThumbnail"+id));
informationContainer.removeChild(document.getElementById("infoThumbnail"+id));
informationContainer.insertBefore(updateInfoThumbnail(oFREvent.target.result, id), informationContainer.firstChild);
mapContainer.appendChild(mapThumbnail);
};
};
function updateMapThumbnail(result, id){
var newThumbnail = document.createElement("img");
newThumbnail.src = result;
newThumbnail.style.maxWidth = "45px";
newThumbnail.style.maxHeight = "45px";
newThumbnail.id = "mapThumbnail" + id;
return newThumbnail;
}
As you can see I added a console.log method there for test purposes. The problem I am facing is that generating mapThumbnail with set max dimensions (45x45) still has the height and width attributes set with the original image size. I tried reading image.height/width and image.style.height/width as well as naturalHeight/width and clientHeight/width.
None of these solutions return the height and width after resizing.
Thanks for your time.
Also, please refrain from offering solutions that require JavaScript libraries.
Edit: forgot to mention that the image placed inside the div is re-sized to the dimensions that I do want it to be. It's just the attributes that seem to be wrong.
There are four different and undependant widths on an image:
1) img.naturalWidth is the width in px the original image file has. It doesn't change when you set the other widths to some value. This value is rendered when the others are not defined.
2) img.width is an attribute of img. You find it inside the html img tag and can set it with img.setAttribute('width', 'value'). It doesn't change when the others are set to some value. This value is rendered when 3) is not defined and 4) is >= img.width or not defined.
3) img.style.width is a css-property of the images style. You can set it in your css or into the style-attribute in the img tag with img.style.width = 'value';. It doesn't change when the others are set to some value. This value is rendered when it is <= 4) or 4) is not defined.
4) img.style.max-width is another css-property of images style. You can set it in your css or into the style-attribute in the img tag with img.style.maxWidth = 'value';. It doesn't change when the others are set to some value. This is rendered when 2) or 3) are not defined or have values > 4).
So you have to decide by yourself which value you want to receive or set.
Its the same with height, there are also four heights.
EDIT According to your comment:
Inside your function updateMapThumbnail you create a new img. A newly created img has no .width unless you define it with newThumbnail.setAttribute('width', 'value). Same with img.style.width: unless you set it explicitely somewhere it's simply not there.
Did you try:
console.log(getComputedStyle(mapThumbnail).width);

Get original dimensions of resized html image element

Is there a simple and efficient way to get the true dimensions (in JavaScript) of an image that is displayed in an <img> element with a potentially different rendered size (e.g. via max-height or max-width)?
There is present naturalWidth and naturalHeight DOM attributes.
For example:
var image = new Image();
image.src = "test.jpg";
image.onload = function() {
alert('width - ' + image.naturalWidth);
alert('height - ' + image.naturalHeight);
}
Or see example on jsFiddle.
More info at MDN

Sizing/stretching images to dimensions known only after page load

On my website, users can upload large images. I display these images like this:
<img id="userImage" src="userImage.ashx?width=740&id=4fc265d4-a83c-4069-8d6d-0fc78ae2840d">
userImage.ashx is a handler that returns image files based on id, so in this example the image for user 4fc265d4-a83c-4069-8d6d-0fc78ae2840d is returned. You can also set other attributes - in this example only width is given. The image is resized so that it is 740px wide.
I set the src of the image in javascript, once the rest of the page has loaded. By doing this I know how wide the image has to be to fill all the available space:
var width = document.getElementById("userImageHolder").getComputedSize().width;
document.getElementById("userImage").src = "flash/userImage.ashx?type=micrositePhoto&id=" + userId + "&width=" + width;
This all works, but the image doesn't load until everything else on the page has loaded. I have a complex solution to a simple problem.
Is there a better way to do this? What is the best way to shrink/stretch images to fill an area that is only known once the page loads?
Figure out what the upper limit is for width and height and generate the image to that size, then use max-width/max-height to allow the browser to auto scale it based on the size of the browser window.
Try to preload your images in a onDOMReady handler, and then insert in an onLoad one. While this can't guarantee the images to be loaded before everything else, they can at least start loading earlier.
Someting like this (using jQuery):
$(document).ready(function(){
var imageArray = [],
imageSrc = [];
//Fill image src array from somewhere
var len = imageSrc.length;
for(var i = 0; i < len; i++){
var img = new Image();
img.src = imageSrc[i];
img.onload = function(){
//Do something with your loaded image
imageArray.push(this);
}
}
});

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