I am experimenting with canvas as part of my HTML5 introduction. This constitutes as assignment work, but I am not asking for any help on the actual coursework at all.
I am trying to write a rendering engine, but having no luck because once the image is drawn on canvas it looks very distorted, and not at the right dimensions of the image itself.
I have made a animation engine that loads images into an array, and then iterates through them at a certain speed. This is not the problem, and I assume is not causing the issue as this was happening when I drawn an image to the canvas without the animation component.
I think this is natural behaviour for images to be scaled/skewed when the window is resized, so I conquered that by simply redrawing the whole thing once the window is resized.
The images I am using are isometric, and drawn at a pixel level. Would this cause the distortion? It seems setting the dimensions on the drawImage() function are not working are all. I am using JavaScript for the manipulation and rendering of the canvas.
I would normally try and work it out myself, but I do not have any time to ponder why because I have no idea why it is even scaling/skewing the image once it is drawn on the canvas. I cannot share the code for obvious reasons. I should also mention, the canvas's dimension is the total width of the viewport, as I am developing a game.
My question is: Has anyone encountered this and how would I correct it?
Thanks for your help.
Seems that you set dimensions of canvas with css.
Try defining them as html attributes. Example:
<canvas id="test" width="100" height="100">Fallback content</canvas>
Edit:
It will set width/height of canvas element to 100/100 pixels.
Yes, the problem was I was setting the canvas's dimensions with CSS. The canvas element is treated like an image, and I was actually scaling the canvas with CSS not resizing it. Thanks for the help. – Mark just now
Related
My topic here is pretty straight forward for a project..
I saw lots of topics on the subject of resizing images into canvas... but what I'm trying to do here is the opposite.
I have a template image that isn't going to change unless it's a different screen size. However; I'd like to make it so the image in the form of a canvas fits inside the template image dimensions. I'd like to think of the template almost like a container, but since I will be using different images with different dimensions it's a little more complex.
I'm trying to make it so the image created inside the canvas element fits regardless of it's size fits proportionately inside the dimensions of the #tee element.
<body>
<div id="obj-container">
<canvas id="obj"></canvas>
<img id="tee" src="https://doc-04-6s-docs.googleusercontent.com/docs/securesc/qhq5e6giuhl9ifpegip5ens14q2k3js8/8krn1u04pvhor8f561eg93ipbn8hjh2e/1569607200000/16313464075852650790/11150445017567734732/0B3ubyt3iIvkaUlpHVEpDTGhjQzg?e=view"></img></div>
Here is an actual example on Codepen https://codepen.io/andrew-squire/pen/JjPqPey
So I have YouTube video thumbnails displayed on a website, but they seem to have letterboxing at the top and bottom. I need to crop this, but I can't just crop x many pixels because of the reponsive design.
How would I crop images dynamically based on their width? Would I have to do it using Javascript during resize? Or is there a simpler approach?
I had a similar issue. I solved it by drawing the image to a canvas, iterating through rows of pixels and checking if they were black. The first time a colored pixel was detected marked the edge of the letterbox. I used this information to crop the image and draw it to another canvas.
It's not a perfect solution, but it worked for me. I hope this helps.
You can use object-fit css but it's not full browser compatible, however a polyfill exist
Else you can use div with background-image and background-size with cover or contain, that have a better support
I'm creating an HTML 5 game using the <canvas> and JavaScript.
In my canvas I'm loading high resolution images. In each Minute there will come some objects to this canvas. If user clicks on it. It'll be removed from the screen.
My issue:
I'm using clearRect() function for clearing the canvas. And again re-draws all images. Is it necessary that each time I re-draw the entire content ? Is there any option to re-draw that particular area ?
When I used the clearRect() to clear the exact area of that object. The background image also got removed. Is there any way to save the particular portion of background image and draw that portion with this saved image ? (Because my objects are moving on the canvas, I need to retreive the image data dynamically)
I'm new to WebTechnology and HTML 5. So please help me. Thanks in advance
There are a few canvas layer libraries that adds support for the layers:
CanvasLayers
CanvasStack
Think of the canvas as a painting, it is not possible to remove a "layer" of content once it has been applied. You can specify a portion of the canvas to clear using clearRect(x,y,height,width), but you will always need to redraw the background of what you deleted. The drawImage() function takes arguments to draw a specific portion of an image in a specific location, but perhaps more along the lines of what you are looking to use is imageData.
I suggest you do some reading up on the canvas here Mozilla Dev Network: Canvas
Usually when an image is being resized in javascript or css3(using background-size), it will stretch an image from the center point. I need an image to be stretched and distorted from a single point that could be anywhere. It's going to be dynamic so I don't want to resort to using separate images.
Here's a pic that illustrates what I mean:
Hopefully there's an answer out there!
You have a few options to achieve this effect.
The "correct" way would be to use canvas to draw the image: Skewing images individually using canvas
Another way would be to fake the effect using the CSS transform skew.
http://developerdrive.com/demo/skewing_elements/skewing_elements.html
You would do this inside an element with "overflow: hidden" to make it look like a background image.
It's not even clear to me what you want from the image you're linking too. Do you want it distorted or not? And is the distortion uniform?
I'm going to guess whatever you're doing can be approximated by drawing an ever decreasing set of (or maybe rectangles) clipped from the center of a some image and drawing them onto a "canvas" (think generic term not html5 term) given new coordinates for the center of each clipping. There may be a faster way to draw this than redrawing parts of the image multiple times, it's just how I visualize it possibly working.. at least maybe in some mathematical sense.
Okay my last question got no response. I think I didn't ask the way I should do.
Basically my requirement is similar to this one Programmatically Clip/Cut image using Javascript
But following that link will result in a rectangle view of any portion of the image but I want to clip it any direction (polygon). Would that be possible?
There is not a good way to make an arbitrary polygon shape with the HTML 4 DOM. If you were using canvas I'd say you could do it that way. Your other option would be to just have a transparent png (and gif for IE6) on top and then the image underneath that and absolute positioned similarly to the other answer you referenced.