I'm working on a page that will allow a webmaster to add styles to their twitter feed. Several of these styles use transparency in their display. I want to create a list of images for them to choose from. Currently I am taking screenshots on a checked background such as this:
But that isn't really what I want.
Is their some method of capturing an image of an HTML element, and maintaining the transparency?
EDIT: I'm just digging into this, so I'm coming across new topics, such as HTML5 Canvas, and -moz-element. Is it possible to set a canvas background to the html element using -moz-element, then extract the image data from the canvas? I'm going to try this unless someone who's 'been there done that' heads me off.
EDIT: The -moz-element and canvas was a deadend. -moz-element will set the item as a background, but will not allow you to save background image. And canvas doesn't save its background, even when the background is a normal image.
It requires a little bit of work, but it is doable, as long as it's HTML you're laying out. You can't recover the transparency of markup in pages you've downloaded without saving those pages and editing them locally. By rendering the HTML elements multiple times, on different background colors, the opacity can be derived using an image editor. You're going to need a decent image editor, I use GIMP.
Render the elements you want to save three times, on a black, a white and a neutral gray background(#888).
Using a screen capture program, capture those displays and crop them to the exact same areas.
In GIMP open those images as layers and order them black, white and gray, top to bottom.
Set the top, black layer to difference mode. This will give a grayscale difference between the black and white layers.
Merge down the top layer. This will leave us with two layers. The gray background layer and the grayscale difference. Invert the colors of the difference layer, and copy it to the clipboard.
Add a layer mask to the gray background layer and paste the clipboard into the layer mask.
Delete the grayscale layer and apply the layer mask on the gray background layer. That should leave one layer with opacity similar to the original.
The opacity is off by a bit, but if we duplicate the layer and merge it with itself, it's right in the ballpark.
It's probably not pixel perfect, but it is proof of concept. Opacity of HTML markup can be captured.
Using Puppeteer makes this much easier to do. It runs a web-page in-memory.
Start a local fileserver - python -m SimpleHTTPServer 8080
Then this script should do the trick:
const puppeteer = require('puppeteer')
;(async () => {
const browser = await puppeteer.launch()
const page = await browser.newPage()
await page.goto('http://localhost:8080/index.html', {
waitUntil: 'networkidle0'
})
const elements = await page.$('body')
await page.evaluate(() => (document.body.style.background = 'transparent'))
await elements.screenshot({ path: 'myImg.png', omitBackground: true })
await browser.close()
})()
the docs for .screenshot() are here.
What you'd need is a web browser that can render into an image buffer in memory instead of the screen.
My guess is that all browsers can do this (that should be part of the renderers) but I'm not aware of any browser where you can access this function, at least not from JavaScript.
If you download the WebKit sources, there should be test cases which do something like that :-/
No, there's no software that will allow you to take screenshots and preserve the transparency of individual visual elements as a transparent spot in the image, because that's not how a screenshot works - screenshots are WYSIWYG, by definition, all elements in your screenshot will always have a non-transparent background.
I think your best bet here is to recreate the desired portion as an image, where you can control the transparency normally. It's not the best solution, but if you're doing this a lot with the same kinds of things, it will be much faster for you rather than cropping/editing screenshots.
Related
I'm trying to replace an image in a Google Slide by a smaller version of it (in terms of bytes).
The smaller image should be displayed exactly the same way than the older.
But when my original image was croped, I cannot reproduce it with the new one.
What I'm doing is simple (I'm using this replace method)
let image = page.getImages()[0];
let newImageUrl = optimize(image.getContentUrl()); // API call to get an optimized image. newImage will have the same width and height
image.replace(newImageUrl, true);
A visual example.
Here is my slide before (pay attention to the "Quick" logo at the bottom right corner)
And here is the result after replacing it (you can see that the bounding box is the same, it takes the same space in the slide, but the image itself is lower)
How can I reproduce the croping that I've initially done in my slide with that button ?
Thanks
Issue:
As mentioned in comments, crop properties are currently read-only, so this cannot be done. Here are possible workarounds: https://stackoverflow.com/a/63256489, https://stackoverflow.com/a/64040404, https://stackoverflow.com/a/67309702.
Feature request:
There's a feature request in Issue Tracker. Anyone interested in this, consider starring it:
Why are Image Crop Properties read only
How can I delay /defer the loading of large background image? The reason am asking this question is because I have a poor score for "first meaningful paint" When I run performance tests on the page. I have tried reducing image size as much as possible.
If it is a background image you can use the Javascript onLoad event. This event excutes only after the whole page is finished loading.
Example:
function loadBGIMG(){
document.getElementById("any-menu").style.backgroundImage="url(../images/any-menu.jpg)";
}
window.onload=loadBGIMG();
First meaningful paint (I'll call it FMP) doesn't have to be an image. If FMP doesn't have to be the background image (it can be a h1, p or other elemnets), you can probably separate the line referencing the image in a separate file so that other components can be painted without being blocked by downloading the image.
I have an animated gif in an img tag that I start by rewriting the src attribute. The gif was created, though, to loop and I only want it to play once. Is there a way, with Javascript or jQuery, to stop an animated gif from playing more than once?
I was having the same problem with an animated gif. The solution is rather simple.
Open the Animated gif in Photoshop.
Go to the Window tab and select timeline(if the timeline is not already open).
At the bottom of the timeline panel, you will find an option, which says "Forever".
Change that to "Once".
Go to File> Export> Export for Web and save it as a gif.
That should do it.
can you find out how long the gif takes to loop once?
if so then you can stop the image like this:
pseudocode:
wait until the end of the image (when it is about to loop)
create a canvas element that has a static version of the gif as currently displayed drawn on it
hide gif
display canvas element in a way that makes it look like the gif froze
javascript:
var c = $("canvas")[0];
var w = c.width;
var h = c.height;
var img = $("img")[0];
setTimeout(function () {
c.getContext('2d').drawImage(img, 0, 0, w, h);
$(img).hide();
$(c).show();
},10000);
jsfiddle
edit:
I forgot to add reference to the original answer that I took this from, sorry
Stopping GIF Animation Programmatically
that one doesn't address the time factor you need for only one loop
Also, it has been mentioned that this approach is problamatic in certain cases (It actually didn't work when I try it in firefox right now...). so here are a few alternatives:
mentioned by Mark: edit the gif itself to avoid looping. this is the best option if you can.
but I've run into cases where it was not an option (like automated generation of images by a third party)
instead of rendering the static image with canvas, keep a static image version and switch to stop looping . this probablyhas most of the problems as the canvas thing
Based on this answer, it's kinda expensive, but it works. Let's say a single loop takes 2 seconds. At a setTimeout after 2 seconds kick in a setInterval, that would reset image source every millisecond:
setTimeout(function() {
setInterval(function() {
$('#img1').attr('src',$('#img1').attr('src'))
},1)
}, 2000)
again, probably just a proof of concept, but here's demo: http://jsfiddle.net/MEaWP/2/
Actually it is possible to make a gif to stop after just one iteration or any specific number of iterations, see an example below (if it is not already stopped), or in jsfiddle.
To do that the gif must be created with number of iterations specified. This could be done using Screen to Gif, it allows to open a gif or a bunch of images and edit it frame by frame.
This solution also allows you to reset the animation by imgElem.src = imgElem.src; but this does not work in MS IE/Edge.
Jurijs Kovzels's answer works in some condition but not in all.
This is browser-dependent.
It works well with Firefox. But In Google Chrome and Safari, it does not work if the gif is on the same server. The example he provided works because the gif is on the external server.
To restart gifs stored on the internal server, using Google Chrome and Safari, you need extra steps to make it work.
const img = document.getElementById("gif");
img.style = "display: none;";
img.style = "display: block;";
setTimeout(() => {
img.src = img.src;
}, 0);
This is inspired by this answer.
Not sure if this is the best way to respond to everyone and have it appear after all the previous answers and comments, but it seems to work.
I don't have much control over the gif. People post whatever gif they want as the "thankyou.gif in their account directory and then the ThankYou code runs whatever they've put there when a comment is submitted to a form they've posted. So some may loop, some may not, some may be short, some may be long. The solution I've come to is to tell people to make them 5 seconds, because that's when I'm going to fade them out, and I don't care if they loop or not.
Thanks for all the ideas.
I know I am pretty late here but..here it is...
I don't know if you would go to this length but let me share a trick.
Open the GIF in Macromedia Flash 8(it has deprecated since then), Export the GIF as Animated GIF. You will have to choose the file location. After that you would receive a dialog box with settings. In that, add the number of times you want the animation to happen. Click OK. Problem solved.
In a Metro App, when retrieving the Thumbnail of a StorageFile using the GetThumbnailAsync() method, the Background Color is a Dark Blue/Navy Blue.
Is it possible to override this Color? I would like the Background to be Transparent.
From the documentation,
The thumbnail is an icon on a background of appropriate size. The background color is determined by the app that is associated with the file.
Combined with the following note:
Note If the associated app is a Windows Store app, the app's tile background color is used.
If your app has an association with the file, just make sure your apps Background color is Transparent (not 100% sure you can do that, actually).
The other option is to use something like WriteableBitmapEx to find every pixel of the tile color, then turn those pixels to Transparent. Shouldn't be too absolutely terrible, but will have an overhead (naturally).
Hope this helps and Happy Coding!
I have been working on a web application for some time now and did notice that the CPU usage was a bit high a long time ago, but the development has been halted for a while.
Recently I started developing again and discovered that the CPU usage goes high after an animated GIF image has been display as the background image.
I use Ajax to update content and apply CSS classes to elements to display a loading indicator. I remove the CSS class when the content has finished loading. If I comment out the classes in the stylesheet that contains the GIFs, everything looks normal.
I have tested it in Internet Explorer 7 and Internet Explorer 8.
What can be done to alliviate this problem?
var blabla = function() {
var element = $('id of element');
element.addClassName('a css classname');
new Ajax.Request({some parameters},
onSuccess: function() {
element.removeClassName('a CSS classname');
....
},
onFailure: function() {
element.removeClassName('a CSS classname');
....
},
onComplete: function() {
element.removeClassName('a CSS classname');
....
}
}
}
It's possible that this issue is related to how Internet Explorer loads data needed from CSS classes. Might I suggest an alternate approach: instead of using the loading animation contained within a CSS class, just put the .gif in a visible <img> tag straight into the HTML. Then, when onSuccess or another method is called, you can just run:
$("#ajax-gif").hide();
As already commented on, it looks like it doesn't have anything to do with the GIF image itself, especially not one at 20x20 pixels.
If you are changing the background of a page with a GIF image, it must redraw what's on top of it to a certain extent.
To bring down the CPU usage, either reduce what's on your page before you change the background or stop using GIF images, it's 2011!
If this problem is only occurring in Internet Explorer, it is indeed the redraw issue that commenters to Barnzy's answer have talked about. It should create similar problems across other browsers as well.
One solution would be to use the JavaScript onload event handler to preload all of your GIF images in the DOM, which would reduce the need to redraw and should stop escalating the CPU cycles.
I agree that in 2011 using GIF images is probably not the best approach for web design.