I'm trying to add KineticJS shapes to an existing pdf file using pdf.js. The problem I have is that KineticJS creates a new canvas and won't use the canvas created by pdf.js. I've tried referencing the pdf.js canvas in KineticJS but that won't work. Any Ideas in how to integrate the two? The main purpose is to provide annotations to the pdf.
If you’re not too far into the process, you might try Bytescout which generates .pdf and also includes a hook to load your canvas image into your pdf.
Everything is done on the client-side, so you can view/edit/view/edit to your heart’s content.
They are here: http://bytescout.com/products/developer/pdfgeneratorsdkjs/index.html (BTW, No sales pitch here--I’m not connected to bytescout in any way!)
Here’s an example from their website that shows an embedded canvas:
function CreatePDF() {
// create BytescoutPDF object instance
var pdf = new BytescoutPDF();
// set document properties: Title, subject, keywords, author name and creator name
pdf.propertiesSet("Sample document title", "Sample subject", "keyword1, keyword 2, keyword3", "Document Author Name", "Document Creator Name");
// set page size
pdf.pageSetSize(BytescoutPDF.A4);
// set page orientation (BytescoutPDF.PORTRAIT = portrait, BytescoutPDF.LANDSCAPE = landscape)
pdf.pageSetOrientation(BytescoutPDF.PORTRAIT);
// add new page
pdf.pageAdd();
// create temporary canvas (you can also simply get existing canvas)
var canvas = document.createElement('canvas');
// set width and height
canvas.width = 320;
canvas.height = 240;
// get context from canvas (to draw on)
var context = canvas.getContext("2d");
// set white background color
context.fillStyle = "#FFFFFF";
// and fill the background with white color
context.fillRect(0, 0, 320, 240);
// draw the yellow circle
context.strokeStyle = "#000000";
context.fillStyle = "#FFFF00";
context.beginPath();
context.arc(100, 100, 50, 0, Math.PI * 2, true);
context.closePath();
context.stroke();
context.fill();
// load image from canvas into BytescoutPDF
pdf.imageLoadFromCanvas(canvas);
// place this image at given X, Y coordinates on the page
pdf.imagePlace(20, 40);
// return BytescoutPDF object instance
return pdf;
}
Related
I have this image drawn to a HTML5 canvas:
What I want to do is apply color to just a part of it.
The part where I want to apply color is defined by the following overlay image:
So, basically, I would like to guide my coloring by the overlay. So where the overlay pixels meets the main image pixels I should apply a color on the main image. At least that's how I see it working.
Notice that the overlay matches the whole image except for the lacing.
The catch is that I would like to retain the main image texture while applying the color. You can see that it has a leather texture and a "real" feel which I want to keep.
Can you please show me some methods of achieving this or share some thoughts?
Thank you!
globalCompositeOperation is your friend here.
Basically, you draw your overlay, then you set the gCO to 'source-atop' composite mode, which will make all your future drawings to only stay where there were already opaque pixels drawn, so it is important that your overlay has transparent parts.
So then you just fill a rectangle of your desired command, and finally you draw your original image, either behind, or blended to the new shape we just created.
var ctx = canvas.getContext('2d');
var loaded = 0;
function onload(){
if(++loaded === 2){
canvas.width = this.width;
canvas.height = this.height;
ctx.font = "40px sans-serif";
draw();
}
}
var original = new Image();
var overlay = new Image();
original.onload = overlay.onload = onload;
original.src = 'https://i.stack.imgur.com/vIKpI.png';
overlay.src = 'https://i.stack.imgur.com/10Tre.png';
// list of blending modes.
// Note that destination-over is a composite mode,
// which place the new drawings behind the already-there ones
var currentMode = 0;
var modes = ['destination-over', 'lighter', 'multiply', 'screen', 'overlay', 'darken',
'lighten', 'color-dodge', 'color-burn', 'hard-light', 'soft-light',
'exclusion', 'hue', 'saturation', 'color', 'luminosity' ];
function draw(){
// switch between different Blending modes
var mode = modes[currentMode];
currentMode = (currentMode+1)%(modes.length);
// clear previous
ctx.clearRect(0,0,canvas.width, canvas.height);
// draw our overlay
ctx.drawImage(overlay, 0,0);
// this will keep new drawings only where we already have existing pixels
ctx.globalCompositeOperation = 'source-atop';
ctx.fillStyle = 'red';
ctx.fillRect(0,0,canvas.width, canvas.height);
// now choose between the list of blending modes
ctx.globalCompositeOperation = mode;
// draw our original image
ctx.drawImage(original, 0,0);
// go back to default
ctx.globalCompositeOperation = 'source-over';
// just so we can know which one is shown
ctx.fillStyle = 'black';
ctx.fillText(mode, 40,40)
// do it again
setTimeout(draw, 1000)
}
canvas{
width: 100%;
}
<canvas id="canvas"></canvas>
I want to have html5 canvas text slide in behind nothing, its an effect where text appears like coming out behind some obstacle, but the obstacle is invisible.
Here is some youtube video showing how to do it in after effect:
https://www.youtube.com/watch?v=KIYMy7vLLRo
I know how to slide a text along canvas, and one idea I got is having two canvases on top of each other, and top canvas is smaller and contains the text that is initially out of canvas and slides in. But if there is a way to do it with just one canvas that would be great.
You can using a clipping path to mask out part of the text.
Save the existing clipping path using the save() method. Create a shape/path and make it the new clipping path using the clip() method. Draw your text. Store the previous clipping path using the restore() method.
For example, suppose your canvas is 100 pixels by 100 pixels. The following will draw text on only the left side of the canvas.
context.save();
context.rect(0, 0, 50, 100);
context.clip();
context.fillText("Draw some text.", 30, 50);
context.restore();
jsFiddle : https://jsfiddle.net/CanvasCode/vgpov2yk/3
var c = document.getElementById('myCanvas');
var ctx = c.getContext("2d");
// Positions for the text startint off
var xText = -100;
var yText = 150;
// This will update the canvas as fast as possible (not good)
setInterval(function () {
// Clear the canvas
ctx.fillStyle = "#F0F";
ctx.fillRect(0, 0, c.width, c.height);
ctx.save()
// We create a clip rect
ctx.rect(200,0,400,400);
ctx.clip();
// Draw text
ctx.fillStyle = "#FFF";
ctx.font = "30px Arial";
ctx.fillText("Hello World", xText, yText);
ctx.restore();
// Increase the text x position
if (xText < 200) {
xText += 0.5;
}
}, 15);
All you have to do is use a clip rect which is like a mask in image editing.
I'm struggling to make smooth image resized in canvas in Chrome. In firefox it works well, but in Chrome I'm stuck on making it smooth.
Here is the jsfiddle
http://jsfiddle.net/flashmandv/oxtrypmy/
var AVATAR_SIZE = 100;
var WHITE_BORDER_SIZE = 3;
var stage = new createjs.Stage("canvas");
var avCont = new createjs.Container();
stage.addChild(avCont);
avCont.x = avCont.y = 20;
//add white circle
var whiteBorderCircle = new createjs.Shape();
var radius = (AVATAR_SIZE+WHITE_BORDER_SIZE*2)/2;
whiteBorderCircle.graphics.beginFill("white").drawCircle(radius, radius, radius);
avCont.addChild(whiteBorderCircle);
//add avatar image mask
var avatarMask = new createjs.Shape();
avatarMask.graphics.beginFill("red").drawCircle(AVATAR_SIZE/2+WHITE_BORDER_SIZE, AVATAR_SIZE/2+WHITE_BORDER_SIZE, AVATAR_SIZE/2);
//add avatar image
var image = new Image();
image.onload = function(){
var bitmap = new createjs.Bitmap(image);
bitmap.mask = avatarMask;
var bounds = bitmap.getBounds();
bitmap.scaleX = (AVATAR_SIZE+WHITE_BORDER_SIZE*2) / bounds.width;
bitmap.scaleY = (AVATAR_SIZE+WHITE_BORDER_SIZE*2) / bounds.height;
avCont.addChild(bitmap);
stage.update();
};
image.src = 'http://files.sharenator.com/sunflowers-s800x800-423444.jpg';
Notice the jagged image
Please help
It is due to how clipping works in Chrome. Clip masks are pretty brutal in Chrome while in Firefox you get anti-aliasing along the non-straight edges.
Here is a proof-of-concept for this (run this in Chrome and in FF to see the difference):
http://jsfiddle.net/r65fcqoy/
The only way to get around this is to use composite modes instead, which basically means you need to rewrite your code unless the library you're using support this in some way.
One use of a composite mode is to use it to fill anything inside an existing drawing on the canvas.
We'll first create the filled circle we want the image to appear inside
Change comp mode to source-in and draw image
Then we go back to normal comp mode and draw the outer border
Here is an approach using vanilla JavaScript where you can control how you plug things together - this is maybe not what you're after but there is really not much option if the library as said doesn't support comp mode instead of clipping:
var canvas = document.getElementById('canvas'),
ctx = canvas.getContext('2d'),
img = new Image,
x = 70, y =70;
var AVATAR_SIZE = 100;
var WHITE_BORDER_SIZE = 3;
var radius = (AVATAR_SIZE+WHITE_BORDER_SIZE*2)/2;
img.onload = function() {
// first draw the circle for the inner image:
ctx.arc(x, y, AVATAR_SIZE*0.5, 0 , 2*Math.PI);
ctx.fill();
// now, change composite mode:
ctx.globalCompositeOperation = 'source-in';
// draw image in top
ctx.drawImage(img, x-AVATAR_SIZE*0.5, y-AVATAR_SIZE*0.5,
AVATAR_SIZE, AVATAR_SIZE);
// change back composite mode to default:
ctx.globalCompositeOperation = 'source-over';
// now draw border
ctx.beginPath();
ctx.arc(x, y, radius + 5, 0, 2*Math.PI);
ctx.closePath();
ctx.lineWidth = 10;
ctx.strokeStyle = '#ffa94e';
ctx.stroke();
};
img.src = 'http://i.stack.imgur.com/PB8lN.jpg';
<canvas id=canvas width=500 height=180></canvas>
Another solution to this would be in onload function to add another shape above the masked image to simply cover the jagged edges of the clipping mask
I have this code that for some reason it should draw canvas many times (using setTimeout):
function drawImage() {
var img = new Image();
var canvas = document.getElementById("event");
var context = canvas.getContext("2d");
img.src = "../img/event.png";
img.onload = function () {
context.drawImage(img, 0, 0);
}
setTimeout(drawImage, 3000);
}
but it cause dark edge as draw more times as this:
Is it possible to prevent edges become dark in repetitively drawing?
As long as the image has an alpha-channel you cannot avoid this when re-painting it over and over without some mechanism to reset the alpha values drawn.
The reason for this is that the alpha-value for that pixel will accumulate so when you draw a non-opaque edge (or anti-aliased edge) on top of each other the value for the alpha channel will be added to the value already drawn resulting in that the edge will be more and more visible.
There are fortunately a couple of ways to avoid this:
A) If you want to keep the alpha-channel in the image use clearRect before drawing the image.
context.clearRect(0, 0, img.width, img.height);
context.drawImage(img, 0, 0);
This will clear the canvas and the alpha channel.
ONLINE DEMO
B) If alpha channel is not important save out the image without any alpha-channel (use PNG with transparency off or use JPEG).
Also a note to your loop in the example - this is not a good way to redraw an image as you are initiating a load/cache check as well as image decoding each time.
You can modify your code as this (adopt as you please):
var canvas = document.getElementById("event");
var context = canvas.getContext("2d");
var img = document.createElement('img'); // due to chrome bug
img.onload = drawImage; // set onload first
img.src = "../img/event.png"; // src last..
function drawImage() {
context.clearRect(0, 0, img.width, img.height);
context.drawImage(img, 0, 0);
setTimeout(drawImage, 3000);
}
I would like to capture a small part of a canvas as a bitmap. Is that possible? This is so that I can replace it after I draw another bitmap on that area. Once I am done with the bitmap I would like to replace the small bit of canvas that I drew on with the original piece.
Thanks!
The drawImage() method of contexts allows you to use an existing canvas as the source. It also allows you to specify sub-regions of the source "image" to draw. You can also create a new canvas element programmatically. Combine these, and you can create your own offscreen buffers and blit to/from them without needing to go through getImageData()/putImageData() or data URLs.
I've put an example of this online.
Note that while the example happens to append the dynamically-created canvas to the document so that you can see it (line 29 of the source), this is not necessary. Canvas elements created in the document function whether attached to the hierarchy or not.
In short:
function copyCanvasRegionToBuffer( canvas, x, y, w, h, bufferCanvas ){
if (!bufferCanvas) bufferCanvas = document.createElement('canvas');
bufferCanvas.width = w;
bufferCanvas.height = h;
bufferCanvas.getContext('2d').drawImage( canvas, x, y, w, h, 0, 0, w, h );
return bufferCanvas;
}
Edit: I benchmarked this technique versus getImageData/putImageData; if speed is important, use drawImage for blitting regions. Here's what I saw:
(source: phrogz.net)
Benchmarks performed by saving and restoring a 125x180 region 10,000 times on OS X on a 2.8GHz Core i7 MacBook Pro. Your mileage may vary. Specifically, saving/restoring regions that are either much larger or smaller may result in different relative performance.
you can do this using .getImageData() and .putImageData()
Example
var canvas, ctx, img, imgd, col;
window.onload = function () {
canvas = document.getElementById('canvas');
ctx = canvas.getContext('2d');
col = {
0: '#000',
.25: '#0099f9',
.55: '#03f',
1: '#000'
};
img = document.getElementById('img');
var w = h = canvas.width = canvas.height = 200;
var grad = ctx.createRadialGradient(w / 2, w / 2, 0, w / 2, w / 2, h);
for (var i in col) {
grad.addColorStop(i, col[i]); //just a funny mess, please don't bother :)
}
ctx.fillStyle = grad;
ctx.fillRect(0, 0, w, h);
imgd = ctx.getImageData(50, 50, 20, 20); //caching the image Data
}
function draw() {
ctx.drawImage(img, 50, 50, 20, 20); //drawing Image on to canvas
}
function redraw() {
ctx.putImageData(imgd, 50, 50, 20, 20); //redraw the cached Image Data
}
and a simple Online Example, just you :)
Try it Here
have a look at a similar question here How to Copy Contents of One Canvas to Another Canvas Locally
What i suggest is write somthing like
var canvas1 = document.getElementById('canvas1');
var src = canvas1.toDataURL("image/png"); // cache the image data source`
to save image in a variable and then retrive it later with
var img = document.createElement('img'); // create a Image Element
img.src = src; //image source
var ctx1 = canvas1.getContext('2d');
ctx2.drawImage(img, 0, 0); // drawing image onto second canvas element
Taken from here