I inserted a canvas element into the DOM of a new file with the following code:
$('#nav_steps').html(canvas);
I want to select this canvas to do something with it, but I can't. Can you help me? Thanks.
data.forEach(function(data) {
var img = new Image();
img.crossOrigin = 'anonymous';
img.onload = function() {
var canvas = document.createElement('canvas');
canvas.width = w_notepad;
canvas.height = h_notepad;
$(canvas).toggle(!data.isActive).appendTo('#canvas_panel');
var ctx = canvas.getContext('2d');
ctx.drawImage(this, 0, 0, w_notepad, h_notepad);
};
img.src = data.dataImageURL;
});
i want :
$("canvas:eq(0)");
Thank.
Related
This piece of code below is supposed to convert the raw image to base64 string.
let base1="";
let base2="";
let base3="";
let base64String="";
var img=new Image();
var img1=new Image();
var img2=new Image();
img.src='Screenshot (1).png';
img1.src='Screenshot (2).png';
img2.src='Screenshot (3).png';
var reader = new FileReader();
reader.onload = function () {
base64String = reader.result.replace("data:", "")
.replace(/^.+,/, "");
}
reader.readAsDataURL(img);
base1=base64String;
reader.readAsDataURL(img1);
base2=base64String;
reader.readAsDataURL(img2);
base3=base64String;
But when I execute the code, I get the following error:
Uncaught TypeError: Failed to execute 'readAsDataURL' on 'FileReader':
parameter 1 is not of type 'Blob'.
Why is that? Please help me fix this.
Because readAsDataURL expects the parameter as Blob. Best method will be to convert to base64 data url using canvas
let base1="";
let base2="";
let base3="";
let base64String="";
var img=new Image();
var img1=new Image();
var img2=new Image();
img.onload = function() {
var canvas = document.createElement("canvas");
canvas.width = img.width;
canvas.height = img.height;
ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0);
base1 = canvas.toDataURL();
}
img.src='Screenshot (1).png';
img1.onload = function() {
var canvas = document.createElement("canvas");
canvas.width = img1.width;
canvas.height = img1.height;
ctx = canvas.getContext('2d');
ctx.drawImage(img1, 0, 0);
base2 = canvas.toDataURL();
}
img1.src='Screenshot (2).png';
img2.onload = function() {
var canvas = document.createElement("canvas");
canvas.width = img2.width;
canvas.height = img2.height;
ctx = canvas.getContext('2d');
ctx.drawImage(img2, 0, 0);
base2 = canvas.toDataURL();
}
img2.src='Screenshot (3).png';
The canvas.toDataURL() without param will generate a data url of type png if if the img src is a jpg
I am trying to create PDF with Image. I have URL of Image as below:
var url = "https://firebasestorage.googleapis.com/v0/b/dicom-poc.appspot.com/o/images%2FNiouCzjBYna8Wx1VO2x3UST5tDc2%2F2020-10-07%2F05%3A03%3A58%2Fvisualization%2FL-CC.png?alt=media&token=dce8859a-3427-432b-8176-590e9569aad9"
and my code is here:
var pdf = new jsPDF();
var img = new Image();
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
img = document.createElement('img');
img.src = url;
img.onload = function(){
canvas.height = img.height;
canvas.width = img.width;
var dataURL = canvas.toDataURL('image/png')
var base64 = dataURL.replace(/^data:.+;base64,/, '');
pdf.text("Hi");
pdf.addImage(base64,'PNG',5,5,50,50);
pdf.save("download.pdf");
}
After running above code PDF is getting downloaded successfully with text "Hi" but image is not there.
I have tried multiple solutions suggested by people but no result.
Could you please guide me for same.
Thanks in advanace!
You did not draw anything on the canvas.
var pdf = new jsPDF();
var img = new Image();
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
img = document.createElement('img');
img.src = url;
img.onload = function(){
canvas.height = img.height;
canvas.width = img.width;
ctx.drawImage(img, img.width, img.width);
var dataURL = canvas.toDataURL('image/png')
var base64 = dataURL.replace(/^data:.+;base64,/, '');
pdf.text("Hi");
pdf.addImage(base64,'PNG',5,5,50,50);
pdf.save("download.pdf");
}
i'm currently trying to load a base64 img into my canvas
console.log('Change');
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var image = new Image();
image.onload = function() {
ctx.drawImage(image, 0, 0);
};
image.src = stack[1].save;
stack[1].save contains a valid base64 png img URL('data:image/png;base64,xxxxxx'), when i paste this URL into my browser i can see a valid img
The fact is that nothing changes and i dont have any error
If you could help me this will be awesome, thank's
Yes the code you have shared should work OK.
Here is an example
const canvas = document.getElementById('canvas')
const ctx = canvas.getContext('2d')
var image = new Image();
image.onload = () => { ctx.drawImage(image, 0, 0) }
image.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAQAAAAngNWGAAAAF0lEQVR42mNk+M9AFGAcVTiqcFQhCAAAf0sUAaSRMCEAAAAASUVORK5CYII="
var image2 = new Image()
image2.onload = () => { for(i=1; i<9; i++) ctx.drawImage(image2, 30*i, 5+4*i) }
image2.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO 9TXL0Y4OHwAAAABJRU5ErkJggg=="
<canvas id="canvas"></canvas>
The only thing that could be wrong is that stack[1].save that you are using...
This is my code:
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 990;
canvas.height = 409;
canvas.style.display='block';
var style=canvas.style;
style.marginLeft="auto";
style.marginRight="auto";
var position=1;
var background = new Image();
background.src="backdrop3.jpg";
var currentImage= new Image();
document.body.appendChild(canvas);
ctx.drawImage(background, 0, 0);
For some reason, nothing appears on my html canvas. Ive already checked that the file for the background is in the same location and it is. What could be the problem?
You need to draw the image onto the canvas after it has loaded, like this:
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 990;
canvas.height = 409;
canvas.style.display='block';
var style=canvas.style;
style.marginLeft="auto";
style.marginRight="auto";
var position=1;
var background = new Image();
background.src="backdrop3.jpg";
// the important bit
background.onload = function () {
ctx.drawImage(background, 0, 0);
}
document.body.appendChild(canvas);
I have following code:
var img = new Image();
canvas = document.getElementById("c");
ctx = canvas.getContext('2d')
canvas2 = document.getElementById("c2");
ctx2 = canvas2.getContext('2d')
img.onload = function () {
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img,0,0);
};
img.src = 'mwq.gif';
var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
ctx2.putImageData(imageData, 0, 0);
and i get image on first canvas element, when i check in console there is imageData, with width, lenght and pixel array, but somehow i can't get that image on another canvas element. I dont think there are typos, i rewrote same code several times, and at the end i stripped it to most minimal version without pixel manipulation, but it's still not working.
Your code isn't called in the onload callback, it's executed before the image is loaded so there is nothing to put.
You could change it to
var img = new Image();
canvas = document.getElementById("c");
ctx = canvas.getContext('2d')
canvas2 = document.getElementById("c2");
ctx2 = canvas2.getContext('2d')
img.onload = function () {
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img,0,0);
var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
ctx2.putImageData(imageData, 0, 0);
};
img.src = 'mwq.gif';