There are lots of scripts and plugins on the web for Javascript image crop/resize. Some using the HTML5 canvas to crop a certain area and storing the image back to the client via DataUrl. But without canvas I tested the jrac jquery plugin, but it only provides the cropping coordinates (x, y, width, height) in the end. There is never called an actual cropping function on the image.
How do I actually use these cropping coordinates on the Javascript image object? Can I only use CSS to show the image like being cropped or can I actually crop data out of that image into a new image in Javascript?
It seems to me that all Image crop plugins only provide a handy UI to get crop coordinates but the actual crop/resize must be done server-side with the image being sent to a php script, is that correct?
My question is the same as this one, that has not been answered yet.
Everything is possible in javascript (well almost everything)
To crop an image you need to side step the DOM and built in image handling API's and decode the image yourself. A lot of extra work involved but there is some help out there. A quick search on github found decoders/encoders for both jpg and png formats Image decoders (I am sure there are plenty more about) so with a little work you should be able to modify them to do some cropping.
What you're asking for is a library to read image data to 2d array of pixels (or a 1d array of pixels in case of the canvas), crop the pixels, and write it back to compressed image data.
Sorry to say but that library is the canvas. You can, of course, use css to fake it but all the image data is still there, you're just choosing to only show part of it.
You can try the below one ,But its using Canvas for rendering,
As of now there is no good lib available without canvas becuase it is very difficult to capture the point you selected and to do processing the thousands and thousands of pixels without Graphics Card ,
Canvas only having the functionality to use Graphics Card
intel and firefox is doing some concepts regarding this to introduce parallel processing in javascript
https://github.com/fengyuanchen/cropper/
Yes this is possible with createImageBitmap
Syntax:
createImageBitmap(image)
createImageBitmap(image, options)
createImageBitmap(image, sx, sy, sw, sh)
createImageBitmap(image, sx, sy, sw, sh, options)
See: https://developer.mozilla.org/en-US/docs/Web/API/createImageBitmap
Related
I'm trying to create a simple 'image editor' using HTML5/Javascript that allows to load an image (.png for instance), draw/move/delete different shapes onto that image, and retrieve the coordinates of these shapes drawn to modify the original image.
I've been reading quite a lot regarding SVG and canvas, and my final thought was to go with SVG, as it's handling all the different object states etc. Looking at different examples of code though I'm not sure anymore if SVG is the right way to go...is it even possible to accomplish what I want using SVG?
Update:
The problem is basically to ensure that the chosen strategy (SVG/canvas) supports loading an image, drawing additional shapes, and retrieving the coordinates in a way that modifications on the original image result in the same picture as shown in the editor.
I am creating an app which uses fabricjs canvas drawing comics. Canvas contains some objects such as rectangles, svg object, and jpeg images. After editing is done, the canvas need to be stored in the server (nodejs) and should be reloaded later from server by the creator or other viewers.
I thought I can serialize canvas to svg string and store svg string on the server and upload images which exist in the canvas one by one to the server as well. Later on, load the svg string replace the images url with the downloaded picture and reload the canvas.
Here are my questions:
1- Is this the right way to achieve my goal?
2- I am doing all of this because my canvas will have different size depending on user device (monitor, smartphone,...) therefore, I chose to use svg for scalability. However, I'm not sure how to scale the original svg string to the new canvas.
Thanks,
Don't save to SVG. SVG is for export. Call myCanvas.toObject()
Not sure how you're going to take advantage of SVG's scalability, if you are just using SVG as a persistence format for canvas. But if you're going to render in SVG, then that makes sense.
You may be overthinking the image solution. How are users going to put an image on the canvas in the first place? The way I do it is to have them upload the image to my server. Then I let them choose images from an image browser. The image they choose already has a URL, so there's nothing left to do when storing/restoring.
I'm currently working on a top-down MMORPG, in JavaScript. As you can imagine, this requires a lot of sprite sheets, and herein lies the problem.
I can simply place the clipped version of a sprite sheet onto the canvas using the canvas.drawImage method. However, this must require more performance than simply loading the clipped version of the image into a new image object which I'd then place onto the canvas using the canvas.drawImage method, as I'd only have to clip it once.
Is this at all possible, and if so, how?
It's a sprite. Any "clipping" is a convenient illusion. Loading a clipped version adds more HTTP traffic which will certainly take more time than drawing canvas image, regardless of the image source, especially when you have the image on the client already.
I'm new to HTML5 and JavaScript, and I'm trying to use the canvas element to create a high(ish) quality output image.
The current purpose is to allow users to all their own images (jpeg, png, svg). this works like a charm. however when I render the image it's always a 32-bit png. how can I create a higher quality picture using JavaScript(preferably) ?
when I output the file, it always seems to keep the same resolution as the canvas, how can I change this using JavaScript(preferably)
Thanks in Advance guys, I looked around for a while but I couldn't find the answer to this :(
If you want to create a larger image with getImageData or toDataURL then you have to:
Create an in-memory canvas that is larger than your normal canvas
Redraw your entire scene onto your in-memory canvas. You will probably want to call ctx.scale(theScale, theScale) on your in-memory context in order to scale your images, but this heavily depends on how they were created in the first place (images? Canvas paths?)
Call getImageData or toDataURL on the in-memory canvas and not your
normal canvas
By in-memory canvas I mean:
var inMem = document.createElement('canvas');
// The larger size
inMem.width = blah;
inMem.height = blah;
Well firstly, when you draw the image to the canvas it's not a png quite yet, it's a simple raw bitmap where the canvas API works on as you call it's methods, then it's converted to a png in order for the browser to display it, and that's what you get when you use toDataURL. When using toDataURL you're able to choose which image format you want the output to be, I think jpeg and bmp are supported along with png. (Don't think of it as a png converted to another format, cause it's not)
And I don't know what exactly do you mean by higher quality by adding more bits to a pixel, you see 32 bits are enough for all RGBA channels to have a true color 8 bits depth giving you way more colors than the human eye can see at once. I know depending on the lighting and angle in which the user is exposed to your picture his perception of the colors may vary but not the quality of it which I'd say only depends on the resolution it has. Anyway the canvas was not designed to work with those deeper colors and honestly that much color information isn't even necessary on any kind of scene you could render on the canvas, that's only relevant for high definition movies and games made by big studios, also, even if you could use deep colors on the canvas it would really depend on the support of the user's videocard and screen which I think the majority of people doesn't have.
If you wish to add information not directly concerned to the color of each pixel but maybe on potencial transformations they could have you better create your own type capable of carrying the imageData acceptable by the canvas API, keeping it's 32-bit format, and the additional information on a corresponding array.
And yes, the output image has the same resolution as the canvas do but there are a couple of ways provided for you to resize your final composition. Just do as Simon Sarris said, create an offscreen canvas which resolution is the final resolution you want your image to be, then, you can either:
Resize the raster image by calling drawImage while providing the toDataURL generated image making use of the resizing parameters
Redraw your scene there, as Simon said, which will reduce quality loss if your composition contains shapes created through the canvas API and not only image files put together
In case you know the final resolution you want it to be beforehand then just set the width and height of the canvas to it, but the CSS width and height can be set differently in order for your canvas to fit in your webpage as you wish.
Can anyone help... how to convert Image to Vectors (SVG) through Javascript.......! Any help will be awesome....!
Three options
Use Online convert's API
http://apiv2.online-convert.com/
Run your own node.js server and use Potrace or AutoTrace
https://www.npmjs.com/package/potrace used by Online convert
https://www.npmjs.com/package/autotrace
Or use imagetracerjs client side.
https://github.com/jankovicsandras/imagetracerjs
This project supports both bitmap to SVG and SVG to bitmap (png/jpeg/gif/etc),offers flexible settings, different renderers, JavaScript API for node.js and browser, and Command line .
If configured correctly it generates good results and small svg size. If you just want to transform logos / drawings then no config is needed but if photographs / realistic paintings then some you need to play with the settings until satisfied with size / quality ratio.
https://www.npmjs.com/package/svg-png-converter
It has a playground although right now I'm working on a better one since more features has been added:
https://cancerberosgx.github.io/demos/svg-png-converter/playground/#
What you're asking isn't really possible. I mean, you could try to do it, but I doubt the results would be particularly satisfying.
SVG to JPEG is a one-way conversion; converting a raster image to a vector image is non-trivial, see this question.
I too was looking for a simple conversion from image to svg - however it is not that easy, but I did find a tool which could take simple images (black and white) and transform them into svg files, also result was much nicer, since it somehow smooth the edges out - however when trying with color images, it did not work.
If you want to make simple images and then later tranform into svg, then using an online converter could help you
I used this to convert a couple of simple .png images to .svg
http://image.online-convert.com/convert-to-svg