How to draw a .bmp file using a canvas tag in html. i found ways to draw a png and jpeg but not bmp files. Can someone suggest me the approaches and also does every browser and platform support bmp files? Please help.
Drawing .bmp file is not limited by the canvas but infact by the browser. Here is a link to the browser image file support list. Besides that if you are new to canvas I am going to point you here to a bunch of fantastic resources on using canvas specifically the section of images about half way down the page. Out of curiosity why are you drawing and image to canvas instead of using an img tag?
Related
I need to compress and rotate the image in the browser. Image sources can be drag'n'drop from a local user or the image can be downloaded from an URL with the same domain as the page with this script. But asking for permission to use HTML5 canvas doesn't fit into the design specification in any way.
The image can be in JPEG, PNG or HEIC format and in the current implementation is stored in Uint8Array. Is it possible to generate a thumbnail or change image orientation without using canvas?
No browser that I know of will ask for permission to use a canvas. Using a canvas is the quickest solution to do this (it's very simple indeed), and HEIC support is easy too: https://alexcorvi.github.io/heic2any/
Need to generate .png images that are about ~20k in size using HTML5 canvas. Unfortunately, when creating .pngs using the toDataURL() method, you cannot specify quality like you can with jpegs.
Any ideas for a workaround? toDataURL seems to be the only way to generate images from Canvas and canvas seems to be the best tool for image processing without server interaction. Appreciate any suggestions.
There IS a way to have compression for PNG images using lossless zlib deflate process http://www.w3.org/TR/PNG-Compression.html . There is a library (https://github.com/ShyykoSerhiy/canvas-png-compression) that provides shim for HTMLCanvasElement.toDataURL() when image type is 'image/png' and enables ability to provide 'quality' as second parameter to HTMLCanvasElement.toDataURL() for png.
NOTE that it provides better results(smaller size) only in Chrome. Firefox sometimes has better compression than canvas-png-compression(as for 0.0.3 version).
You can do something by scaling it down and then scaling it up again.
Scale down by drawing it on a smaller canvas, then get the data url.
Create an image object set the data url as its source.
Draw on the original canvas with this img object (obviously inside the onload event callback)
Find the size ratio of the canvases to give you optimum result by experimenting a bit.
Is there a way to draw partially loaded progressive Image objects (PNG, JPG) into canvas?
Most browsers support progressive loading in the tag, but I can't find how it can be controlled in within canvas.
The answer is no, as per the specification's orders.
If a browser does happen to do this, it is against the spec, which states:
If the image isn't yet fully decoded, then nothing is drawn.
When an img element is in the completely available state and the user agent can decode the media data without errors, then the img element is said to be fully decodable.
You can take a look at streamingtextures js lib
which use custom decoding of progressive JPEG images (via Emscripten version of libjpeg) and return image content as an array of bytes.
This method is used with WebGL but could be also used for 2D canvas and extended to support also GIF, PNG and WebP
I am using HTML5 and javascript in a project. I am loading image from a Url(seleted by user) and then i am moving that image inside canvas. On moving i am redrawing the whole image. But on moving image is flickering. So i want to copy that file from URL to my working directory. So that flickering of image on moving would get stop.
Is there any other way to do this? if not then how can i copy that image file in my working follder(i.e. destination path).
Thanks a lot in advance.
This article will give you some good pointers to optimizing your canvas code. Make sure you take a good look at the section titled: Pre-render to an off-screen canvas.
You probably are facing crossdomain limitations when using images in canvas.
The image and the html document must reside on the same server/domain
otherwise you have to base64 encode the image as the image source.
I have an small drawing application made in processing.js. I would like to save the image made using the application to a server using a php file (no problem on this).
I know the canvas element has a method to get that content, canvas.toDataURL() but I dont know how to do the same with processing.js
Any hint?
Cheers!
perhaps
var image = document.getElementsByTagName("canvas")[0].toDataURL();
So when you use saveFrame() in processing.js. The image opens in a new window and i found it hard to intercept the data. The soultion is to get the image from the canvas in javascript.
// this grabs the canvas and turns it into a base64 image
var image = document.getElementsByTagName("canvas")[0].toDataURL();
// Log the data to the canvas to check it working
console.log(image);
// then you can place the image on your web page
document.getElementById("theImage").src=image;
Then the html is easy. Just add
<img id="theImage"></img>
If you want to upload the image to a server you can acsess the data in js with.
image
Note that you can also use style display:none; and have the canvas render image for you without the canvas displaying. It also supports transparent pngs and the canvas by default is transparent