Develop Reference

Loss of FPS using mask

'm working on an application which allows to make image processing, so I used Javascript and PixiJS library to make it possible. I wanted to update cursor image when canvas was hovered
first solution I tried to use cursor: url(cursor1.png) 4 12, auto; but I can't resize cursor. The default size is 64px and I can't set another value.
second solution I decided to add into DOM and update x,y position using Javascript but I got latency.
third solution was to integrate cursor inside my canvas.
last solution I tried to split actions into 2 canvas. The first deals with image processing and the second is my cursor.
With all propositions made before I got loss of FPS when canvas is hovered excepted the first one.
Init main canvas for image processing
function _initMainCanvas(imgData) {
let newCanvas = new PIXI.Application({
width: imgData.width,
height: imgData.height,
transparent: true
});
let blurContainer = new PIXI.Container();
filters.initFilters();
// ----------------------------------------------------------------------------------------
// Normal Sprite
// ----------------------------------------------------------------------------------------
let bg = main.createSprite({
from: imgData.img,
interactive: true,
filters: [filters.getFilterSharpen(), filters.getFilterAdjustment()],
width: imgData.width,
height: imgData.height
});
newCanvas.stage.addChild(bg);
//$(".blur_cursor").remove();
// ----------------------------------------------------------------------------------------
// Blur Sprite
// ----------------------------------------------------------------------------------------
let bgBlured = main.createSprite({
from: imgData.img,
interactive: false,
filters: filters.getFilters(),
width: imgData.width,
height: imgData.height
});
blurContainer.addChild(bgBlured);
blurContainer.mask = containers.getBlurs();
newCanvas.stage.addChild(blurContainer);
newCanvas.stage.addChild(blurContainer);
select.initSelectionRect();
newCanvas.stage.addChild(select.getSelectionRect());
canvas.addMainCanvas(newCanvas);
document.getElementById("container").appendChild(newCanvas.view);
}
Init canvas for cursor update when mouse hover it
function _initCursorCanvas(imgData) {
let cursorCanvas = new PIXI.Application({
width: imgData.width,
height: imgData.height,
transparent: true
});
_fillCursorCanvas(cursorCanvas);
canvas.addCursorCanvas(cursorCanvas);
document.getElementById("container").appendChild(cursorCanvas.view);
}
function _fillCursorCanvas(cursorCanvas) {
// emptySprite allows to bind events
let emptySprite = new PIXI.Sprite();
emptySprite.interactive = true;
emptySprite.width = cursorCanvas.screen.width;
emptySprite.height = cursorCanvas.screen.height;
cursorCanvas.stage.addChild(emptySprite);
emptySprite
.on("pointerdown", canvasEvents.handlerMousedown)
.on("pointerup", canvasEvents.handlerMouseup)
.on("pointermove", canvasEvents.handlerMousemove)
.on("pointerout", canvasEvents.handlerMouseout);
const scale = W / canvas.getWidth();
const cursorTexture = new PIXI.Texture.from(
urlManager.replace("index.php/", "") + "assets/images/cursor_img/50.png"
);
let circle = new PIXI.Sprite(cursorTexture);
circle.width = 50 / scale;
circle.height = 50 / scale;
cursorCanvas.stage.addChild(circle);
}
Mousemove event
const x = e.data.global.x;
const y = e.data.global.y;
cursor.updatePosition(x, y, W);
Will anyone know how to optimize FPS on mouse flying, thank you in advance !

Why do you need a second canvas just for that?
If you want to update the cursor do it at the end of the update loop and that's it, don't make a new canvas just for that.

Page with multiple chart.js charts to pdf

I have used chart.js to generate a report page that has multiple charts. I need to export this report to PDF. There are many solutions available via search, but I cannot find one which has multiple canvas elements.
The only available solution seems to be to loop through all the images, and recreate the report using the images, and then download that as a pdf.
Is there any simpler/more efficient way to accomplish this?
<body>
<h1> Chart 1 </h1>
<div style="width:800px; height:400px;">
<canvas id="chart_1" width="50" height="50"></canvas>
</div>
<h1> Chart 2 </h1>
<div style="width:800px; height:400px;">
<canvas id="chart_2" width="50" height="50"></canvas>
</div>
<h1> Chart 3 </h1>
<div style="width:800px; height:400px;">
<canvas id="chart_3" width="50" height="50"></canvas>
</div>
</body>

Honestly, it seems like the easiest approach would be to just provide a "download to PDF" link that pops up the browser's print page and instruct to user to select "print as pdf".
If that approach doesn't work for you (or your users), then here is a rough way to do it.
Basically, we create a new canvas element that is the size of your report page and incrementally paint the pixels from your existing chart.js canvas charts into the new canvas. Once that is done, then you can use jsPDF to add the new canvas to a pdf document as an image and download the file.
Here is an example implementation that does just that.
$('#downloadPdf').click(function(event) {
// get size of report page
var reportPageHeight = $('#reportPage').innerHeight();
var reportPageWidth = $('#reportPage').innerWidth();
// create a new canvas object that we will populate with all other canvas objects
var pdfCanvas = $('<canvas />').attr({
id: "canvaspdf",
width: reportPageWidth,
height: reportPageHeight
});
// keep track canvas position
var pdfctx = $(pdfCanvas)[0].getContext('2d');
var pdfctxX = 0;
var pdfctxY = 0;
var buffer = 100;
// for each chart.js chart
$("canvas").each(function(index) {
// get the chart height/width
var canvasHeight = $(this).innerHeight();
var canvasWidth = $(this).innerWidth();
// draw the chart into the new canvas
pdfctx.drawImage($(this)[0], pdfctxX, pdfctxY, canvasWidth, canvasHeight);
pdfctxX += canvasWidth + buffer;
// our report page is in a grid pattern so replicate that in the new canvas
if (index % 2 === 1) {
pdfctxX = 0;
pdfctxY += canvasHeight + buffer;
}
});
// create new pdf and add our new canvas as an image
var pdf = new jsPDF('l', 'pt', [reportPageWidth, reportPageHeight]);
pdf.addImage($(pdfCanvas)[0], 'PNG', 0, 0);
// download the pdf
pdf.save('filename.pdf');
});
You can see it in action at this codepen.
Now let's talk about some gotchas with this approach. First, you have to control the position of each chart.js canvas in the new canvas object. The only way to do that is to have an understanding of how your report page is structured and implement that same structure. In my example, my charts are in a 2x2 grid and the logic handles this accordingly. If you had a 3x2 grid or something different then you would have to change the positioning logic.
Lastly, the final pdf output file dimensions are much larger than the original chart page (from the web). I think the reason is because my chart "container" div stretches across the full page. Therefore, you probably want to use a different approach for setting the size of your new canvas.
So long story short, the above example is meant to demonstrate an approach and not be your final solution.
Good luck!

I have a working solution in vanilla javascript(although I used ts typing) and using the lib jsPdf, where you need a plot per pdf page:
let index = 1;
// create new pdf object
// if don't choose compress as true you will end up with a large pdf file
let pdf = new jsPDF({
orientation: 'landscape',
unit: 'px',
format: 'a4',
compress: true,
})
// search for the html element(s) you need
const canvas = document.querySelectorAll("canvas");
// here my size are in pixels since I configured that in the obj instance
let pageWidth = 400;
let pageHeight = 400;
let index = 1;
// traverse the array of canvas
canvas.forEach( (canva:HTMLCanvasElement) => {
// I added some options among others I added the type of the compression
// method: FAST
pdf.addImage(canva, 'PNG', 10, 10, pageWidth, pageHeight, `img${index}`, "FAST");
// so as to not end up with an extra pdf page at the end of the iteration
if (index < canvas.length) {
pdf.addPage();
}
index++;
});
// download the pdf
pdf.save('Reporte.pdf');

Gridstack - widget's max width bigger than grid width crashes resizing of widget

I'm using gridstack.js (v0.2.6) library for my dashboard view in web application. I tried to implement a possibility to let user change the grid width. Almost everything seems to be working, but I encountered a problem with maxWidth of widgets. Setting widget's maxWidth to bigger value than number of grid columns seems to be crashing resizing of widget. For example, when I set gridWidth = 3 and widget's maxWidth = 5, I can resize widget to max ~1.3 * column width instead of 3 columns.
I provide the most important parts of code:
HTML
<div class="grid-stack grid-stack-3">
</div>
Javascript
Initialization:
var $dashboard = $('.grid-stack');
var columnsNumber = 3;
function initGridStack() {
$dashboard[0].className = "grid-stack grid-stack-" + columnsNumber;
var options = {
cell_height: 200,
vertical_margin: 10,
animate: true,
width: columnsNumber,
draggable: {
handle: '.widget-header',
}
};
$dashboard.gridstack(options);
Adding widget:
// ...
$widget = createWidgetElement()
$dashboard.data('gridstack').addWidget($widget, x, y, width, height, autoposition, minWidth, maxWidth, minHeight, maxHeight);
Question
Has anybody had a similar problem and has any idea how can I handle this? I'll be grateful for any help.

Using jspdf to save html page as pdf, saved pdf contains incomplete page content if browser is zoomed, Why?

I am using jspdf and html2canvas combination to save html page as pdf. A pdf copy of current page is saved the moment you click a button. The problem is, if you zoom in the page, and then click the button, the saved pdf contains incomplete portion of the current page. Most of the part not visible on page due to zooming, gets cut off in the saved pdf page. What is the solution?
Below is the js code being invoked upon click of save button-
var pdf = new jsPDF('l', 'pt', 'a4');
var source = $('#someId')[0];
var options = {
background : '#eee'
};
pdf.addHTML(source, options, function(){
pdf.save('abcd.pdf');
});
EDIT
Taking idea from Saurabh's approach, I tried quite a similar thing, but without writing code for any extra div element. Before saving to pdf I made the screen size of a fixed width, and after printing I brought back the width back to default normal. It is working fine for, if it fails, we can always fix the height of the screen too, so that it appears fine in generated pdf despite zooming. Below is the code used by me:-
var pdf = new jsPDF('l', 'pt', 'a4');
var source = $('#someId')[0];
var options = {
background : '#eee'
};
var width = source.clientWidth;
source.style.width = '1700px';
pdf.addHTML(source, options,
function(){
pdf.save('abcd.pdf');
source.style.width = width+'px';
});

Here is how I managed to get the full page pdf while the page is zoomed in using jsPDF's new .html() method. First, I force the page zoom level back to 100% before converting it to pdf. It's important to reset the scale in html2canvas option after that, otherwise it'll returns a blank page.
<script src="https://cdnjs.cloudflare.com/ajax/libs/jspdf/1.5.3/jspdf.debug.js"
integrity="sha384-NaWTHo/8YCBYJ59830LTz/P4aQZK1sS0SneOgAvhsIl3zBu8r9RevNg5lHCHAuQ/"
crossorigin="anonymous"></script>
<script src="https://html2canvas.hertzen.com/dist/html2canvas.min.js"></script>
<!-- html2canvas 1.0.0-alpha.11 or higher version is needed -->
<script>
function download() {
// Bring the page zoom level back to 100%
const scale = window.innerWidth / window.outerWidth;
if (scale != 1) {
document.body.style.zoom = scale;
}
let pdf = new jsPDF('p', 'pt', 'a4');
pdf.html(document.getElementById('idName'), {
html2canvas: {
scale: 1 // default is window.devicePixelRatio
},
callback: function () {
// pdf.save('test.pdf');
window.open(pdf.output('bloburl')); // to debug
}
});
}
</script>
Update: A better way is to adjust the html2canvas.scale according to the scale factor.
function download() {
let pWidth = pdf.internal.pageSize.width; // 595.28 is the width of a4
let srcWidth = document.getElementById('idName').scrollWidth;
let margin = 18; // narrow margin - 1.27 cm (36);
let scale = (pWidth - margin * 2) / srcWidth;
let pdf = new jsPDF('p', 'pt', 'a4');
pdf.html(document.getElementById('idName'), {
x: margin,
y: margin,
html2canvas: {
scale: scale,
},
callback: function () {
window.open(pdf.output('bloburl'));
}
});
}

I was going through the same problem,
To do this what I did is I made a copy of printing div and while clicking print button I attached div copy to my dom with margin-top:500px
After I got its image then I hide this copy of the div, and set margin-top:0px
I hope this will work for you.

Paper.js Subraster Selecting Wrong Area

I'm working in a Paper.js project where we're essentially doing image editing. There is one large Raster. I'm attempting to use the getSubRaster method to copy a section of the image (raster) that the user can then move around.
After the raster to edit is loaded, selectArea is called to register these listeners:
var selectArea = function() {
if(paper.project != null) {
var startDragPoint;
paper.project.layers[0].on('mousedown', function(event) { // TODO should be layer 0 in long run? // Capture start of drag selection
if(event.event.ctrlKey && event.event.altKey) {
startDragPoint = new paper.Point(event.point.x + imageWidth/2, (event.point.y + imageHeight/2));
//topLeftPointOfSelectionRectangleCanvasCoordinates = new paper.Point(event.point.x, event.point.y);
}
});
paper.project.layers[0].on('mouseup', function(event) { // TODO should be layer 0 in long run? // Capture end of drag selection
if(event.event.ctrlKey && event.event.altKey) {
var endDragPoint = new paper.Point(event.point.x + imageWidth/2, event.point.y + imageHeight/2);
// Don't know which corner user started dragging from, aggregate the data we have into the leftmost and topmost points for constructing a rectangle
var leftmostX;
if(startDragPoint.x < endDragPoint.x) {
leftmostX = startDragPoint.x;
} else {
leftmostX = endDragPoint.x;
}
var width = Math.abs(startDragPoint.x - endDragPoint.x);
var topmostY;
if(startDragPoint.y < endDragPoint.y) {
topmostY = startDragPoint.y;
} else {
topmostY = endDragPoint.y;
}
var height = Math.abs(startDragPoint.y - endDragPoint.y);
var boundingRectangle = new paper.Rectangle(leftmostX, topmostY, width, height);
console.log(boundingRectangle);
console.log(paper.view.center);
var selectedArea = raster.getSubRaster(boundingRectangle);
var selectedAreaAsDataUrl = selectedArea.toDataURL();
var subImage = new Image(width, height);
subImage.src = selectedAreaAsDataUrl;
subImage.onload = function(event) {
var subRaster = new paper.Raster(subImage);
// Make movable
subRaster.onMouseEnter = movableEvents.showSelected;
subRaster.onMouseDrag = movableEvents.dragItem;
subRaster.onMouseLeave = movableEvents.hideSelected;
};
}
});
}
};
The methods are triggered at the right time and the selection box seems to be the right size. It does indeed render a new raster for me that I can move around, but the contents of the raster are not what I selected. They are close to what I selected but not what I selected. Selecting different areas does not seem to yield different results. The content of the generated subraster always seems to be down and to the right of the actual selection.
Note that as I build the points for the bounding selection rectangle I do some translations. This is because of differences in coordinate systems. The coordinate system where I've drawn the rectangle selection has (0,0) in the center of the image and x increases rightward and y increases downward. But for getSubRaster, we are required to provide the pixel coordinates, per the documentation, which start at (0,0) at the top left of the image and increase going rightward and downward. Consequently, as I build the points, I translate the points to the raster/pixel coordinates by adding imageWidth/2 and imageHeight/2`.
So why does this code select the wrong area? Thanks in advance.
EDIT:
Unfortunately I can't share the image I'm working with because it is sensitive company data. But here is some metadata:
Image Width: 4250 pixels
Image Height: 5500 pixels
Canvas Width: 591 pixels
Canvas Height: 766 pixels
My canvas size varies by the size of the browser window, but those are the parameters I've been testing in. I don't think the canvas dimensions are particularly relevant because I'm doing everything in terms of image pixels. When I capture the event.point.x and event.point.y to the best of my knowledge these are image scaled coordinates, but from a different origin - the center rather than the top left. Unfortunately I can't find any documentation on this. Observe how the coordinates work in this sketch.
I've also been working on a sketch to illustrate the problem of this question. To use it, hold Ctrl + Alt and drag a box on the image. This should trigger some logging data and attempt to get a subraster, but I get an operation insecure error, which I think is because of security settings in the image request header. Using the base 64 string instead of the URL doesn't give the security error, but doesn't do anything. Using that string in the sketch produces a super long URL I can't paste here. But to get that you can download the image (or any image) and convert it here, and put that as the img.src.

The problem is that the mouse events all return points relative to 0, 0 of the canvas. And getSubRaster expects the coordinates to be relative to the 0, 0 of the raster item it is extracting from.
The adjustment needs to be eventpoint - raster.bounds.topLeft. It doesn't really have anything to do with the image width or height. You want to adjust the event points so they are relative to 0, 0 of the raster, and 0, 0 is raster.bounds.topLeft.
When you adjust the event points by 1/2 the image size that causes event points to be offset incorrectly. For the Mona Lisa example, the raster size (image size) is w: 320, h: 491; divided by two they are w: 160, h: 245.5. But bounds.topLeft of the image (when I ran my sketch) was x: 252.5, y: 155.5.
Here's a sketch that shows it working. I've added a little red square highlighting the selected area just to make it easier to compare when it's done. I also didn't include the toDataURL logic as that creates the security issues you mentioned.
Here you go: Sketch
Here's code I put into an HTML file; I noticed that the sketch I put together links to a previous version of the code that doesn't completely work.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Rasters</title>
<script src="./vendor/jquery-2.1.3.js"></script>
<script src="./vendor/paper-0.9.25.js"></script>
</head>
<body>
<main>
<h3>Raster Bug</h3>
<div>
<canvas id="canvas"></canvas>
</div>
<div id="position">
</div>
</main>
<script>
// initialization code
$(function() {
// setup paper
$("#canvas").attr({width: 600, height: 600});
var canvas = document.getElementById("canvas");
paper.setup(canvas);
// show a border to make range of canvas clear
var border = new paper.Path.Rectangle({
rectangle: {point: [0, 0], size: paper.view.size},
strokeColor: 'black',
strokeWidth: 2
});
var tool = new paper.Tool();
// setup mouse position tracking
tool.on('mousemove', function(e) {
$("#position").text("mouse: " + e.point);
});
// load the image from a dataURL to avoid CORS issues
var raster = new paper.Raster(dataURL);
raster.position = paper.view.center;
var lt = raster.bounds.topLeft;
var startDrag, endDrag;
console.log('rb', raster.bounds);
console.log('lt', lt);
// setup mouse handling
tool.on('mousedown', function(e) {
startDrag = new paper.Point(e.point);
console.log('sd', startDrag);
});
tool.on('mousedrag', function(e) {
var show = new paper.Path.Rectangle({
from: startDrag,
to: e.point,
strokeColor: 'red',
strokeWidth: 1
});
show.removeOn({
drag: true,
up: true
});
});
tool.on('mouseup', function(e) {
endDrag = new paper.Point(e.point);
console.log('ed', endDrag);
var bounds = new paper.Rectangle({
from: startDrag.subtract(lt),
to: endDrag.subtract(lt)
});
console.log('bounds', bounds);
var sub = raster.getSubRaster(bounds);
sub.bringToFront();
var subData = sub.toDataURL();
sub.remove();
var subRaster = new paper.Raster(subData);
subRaster.position = paper.view.center;
});
});
var dataURL = ; // insert data or real URL here
</script>
</body>
</html>