I'm trying to get random image from input video file, and then put the image into opencv to get grayScale image on the webpage.
Getting random image from video is solved by below-solution.
Javascript how to extract frame from video?
but now i'm stuck to the problem, Is it impossible to give base 64 source image file into opencv(imread, imshow, cv.cvtColor)? Please help me.
'''
//const cv = require("./js/opencv");
var video = document.createElement("video");
var image = new Image();
var canvas = document.getElementById("prevImgCanvas");
var canvas_after = document.getElementById("canvas_after");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
video.addEventListener('loadeddata', function() {
reloadRandomFrame();
}, false);
video.addEventListener('seeked', function() {
var context = canvas.getContext('2d');
context.drawImage(video, 0, 0, canvas.width, canvas.height);
const dataurl = canvas.toDataURL("image/jpeg")
image.src = dataurl;
image.onload = function(){
console.log(image);
let mat = cv.imread(image);
cv.imshow('canvasOutput', mat);
mat.delete();
};
}, false);
var playSelectedFile = function(event) {
var file = this.files[0];
var fileURL = URL.createObjectURL(file);
video.src = fileURL;
}
var input = document.getElementById('fileinput');
input.addEventListener('change', playSelectedFile, false);
function reloadRandomFrame() {
if (!isNaN(video.duration)) {
var rand = Math.round(Math.random() * video.duration * 1000) + 1;
video.currentTime = rand / 1000;
}
}
'''
let image = new Image()
image.src = 'your base64'
await new Promise(r => {
image.onload = r
})
cv.imread(image)
Related
I use "dom-to-image" to convert html table to png:
var wrapper = document.getElementById('exportContent');
domtoimage.toSvg(wrapper).then(function (svgDataUrl) {
downloadPNGFromAnyImageSrc(svgDataUrl);
});
function downloadPNGFromAnyImageSrc(src)
{
var img = new Image;
img.onload = function(){
var canvas = convertImageToCanvas(img);
var pngImage = convertCanvasToImage(canvas);
var anchor = document.createElement('a');
anchor.setAttribute('href', pngImage.src);
anchor.setAttribute('download', 'image.png');
anchor.click();
};
img.src = src;
// Converts image to canvas; returns new canvas element
function convertImageToCanvas(image) {
var canvas = document.createElement("canvas");
canvas.width = image.width;
canvas.height = image.height;
canvas.getContext("2d").drawImage(image, 0, 0);
return canvas;
}
// Converts canvas to an image
function convertCanvasToImage(canvas) {
var image = new Image();
image.src = canvas.toDataURL("image/png", 1.0);
return image;
}
}
It converts the element to png. However I need to put it into doc file.
Now I need to generate/save a docx file with this png without saving png.
How can I do it?
I followed this post: dom to img
So I know this question has been asked before; however, for some reason I cannot get the height and width of my canvas to display correctly.
Here is what I currently have, but for some reason the image gets cut off and does not display the entire image. Any thoughts? Thanks!
function mergeImages(source1, source2){
let image1 = new Image();
image1.src = source1;
var c = document.createElement('canvas');
var ctx = c.getContext("2d");
image1.onload = function (){
c.width = image1.width;
ctx.drawImage(image1, 0, 0, image1.width, image1.height);
let image2 = new Image();
image2.src = source2;
image2.onload = function (){
ctx.drawImage(image2, 0, image1.height, image2.width, image2.height);
console.log(c.toDataURL("image/png"));
};
};
}
You are making the assumption that image1 is loaded before image2, this might be 99% true.
I suggest you get the images first and then write it to the canvas. In your current code you are setting the width and not the height
Attaching two solutions
This is based on what you have, with just some changes around canvas width and height
function mergeImages(source1, source2){
let image1 = new Image();
image1.src = source1;
var c = document.getElementById('canvas');
var ctx = c.getContext("2d");
image1.onload = function (){
let image2 = new Image();
image2.src = source2;
image2.onload = function (){
c.width = Math.max(image1.width, image2.width)
c.height = image1.height + image2.height
ctx.drawImage(image1, 0, 0, image1.width, image1.height);
ctx.drawImage(image2, 0, image1.height, image2.width, image2.height);
console.log(c.toDataURL("image/png"));
};
};
}
mergeImages('https://i.imgur.com/5HtV0Nv.jpg', 'https://i.imgur.com/5HtV0Nv.jpg')
This is based on promises
function loadImage(url) {
return new Promise(resolve => {
const img = new Image();
img.addEventListener('load', () => {
resolve(image);
});
img.src = url;
});
}
async function asyncMergeImages(source1, source2){
let c = document.getElementById('canvas');
let ctx = c.getContext("2d");
let image1 = await loadImage(source1)
let image2 = await loadImage(source2)
c.width = Math.max(image1.width, image2.width)
c.height = image1.height + image2.height
ctx.drawImage(image1, 0, 0, image1.width, image1.height);
ctx.drawImage(image2, 0, image1.height, image2.width, image2.height);
console.log("async",c.toDataURL("image/png"));
}
asyncMergeImages('https://i.imgur.com/csFntM8.jpg', 'https://i.imgur.com/5HtV0Nv.jpg')
I am trying to merge multiple images while retrieving the images from desk. It was taken from "How to create an image generator for combining multiple images?". It's working fine if single image is uploaded, but not working in case of multiple images.
This is my HTML code
<input id="file-input" type="file" name="images[]" multiple maxlength="5" ngf-select="UploadFiles($files)" accept=".png,.jpg,.jpeg,.gif" />
<canvas id="canvas"></canvas>
This is javascript code
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var lastImage;
var lastHeight = 0;
var lastWidth = 0;
var imagesLoaded = 0;
function max(a, b) {
if (a > b)
return a;
return b;
}
function addToCanvas(img) {
canvas.height = max(lastHeight, img.width);
canvas.width = lastWidth + img.height;
ctx.clearRect(0, 0, canvas.width, canvas.height);
if (lastImage) {
ctx.drawImage(lastImage, 0, canvas.height - lastImage.height);
}
ctx.rotate(270 * Math.PI / 180); // rotate the canvas to the specified degrees
ctx.drawImage(img, -canvas.height, lastWidth);
lastImage = new Image();
lastImage.src = canvas.toDataURL();
lastWidth += img.height;
lastHeight = canvas.height;
imagesLoaded += 1;
}
$scope.UploadFiles = function (files) {
$scope.SelectedFiles = files;
cnt = files.length;
console.log($scope.SelectedFiles);
for (i = 0; i < $scope.SelectedFiles.length; i++) {
console.log(files[i]);
var reader = new FileReader();
reader.onload = function (event) {
var img = new Image();
img.onload = function () {
addToCanvas(img);
}
img.src = reader.result;
}
reader.readAsDataURL(files[i]);
}
};
When I select images from the folder, the console's debugger stops at img.onload event, where I am trying to do action in loop.
For loop iteration not working for imageload functions..
files.map((file) => {
var reader = new FileReader();
reader.onload = (event) => {
var img = new Image();
img.onload = () =>
{
addToCanvas(img);
}
img.src = reader.result;
}
reader.readAsDataURL(file);
}
)
I need to read the image data from an image object in javascript.
But my code returns always a blank array (set to 255)
<html>
<header>
</header>
<body>
<input type="file" id="imgfile" onchange="testImageData(event);" />
<canvas id="canvas1" width="640" height="480"></canvas>
<script src="./../scripts/cam.js" ></script>
</body>
</html>
Here is the script
var canvas1 = document.getElementById('canvas1');
var context1 = canvas1.getContext('2d');
function getImageData(image){
/*
returns Uint8ClampedArray object
takes an image obj
*/
var canvas = document.createElement("canvas");
canvas.height = image.height;
canvas.width = image.width;
var ctx = canvas.getContext("2d");
ctx.width = image.width;
ctx.height = image.height;
ctx.drawImage(image,0,0);
return ctx.getImageData(0, 0, ctx.width, ctx.height);
}
function testImageData(event){
var selectedFile = event.target.files[0];
var reader = new FileReader();
var img = new Image();
reader.onload = function(event) {
console.log('onload');
img.src = event.target.result;
img.onload = function(){
context1.drawImage(img, 0,0, img.width, img.height);
var imgData = getImageData(img);
// console.log(imgData);
var data = imgData.data;
for(var i = 0; i<data.length;i+=4){
console.log(data[i],data[i+1],data[i+2],data[i+3]);
}
}
};
In my understanding, the console.log should return me the data in RGBA.
But I'm just getting 255.
console.log output
EDIT:
Okay I found a work around but I don't understand why this is working.
Instead using getImageData, I get the data directly from the drawn context1.
function testImageData(event){
var selectedFile = event.target.files[0];
var reader = new FileReader();
var img = new Image();
reader.onload = function(event) {
console.log('onload');
img.src = event.target.result;
img.onload = function(){
context1.drawImage(img, 0,0, img.width, img.height);
var imgData = context1.getImageData(0,0,img.width,img.height);
var data = imgData.data;
for(var i = 0; i<data.length;i+=4){
console.log(data[i],data[i+1],data[i+2],data[i+3]);
}
}
};
So the problem must lie in creating a new canvas.
You should wait for the image to load img.onload you are waiting for the readers onload event...
you also forget to read the file... missed reader.readAsDataURL
but you don't need the filereader.
window.URL = window.URL || webkitURL
var img = new Image();
img.src = URL.createObjectURL(file)
img.onload = function(){
// put your image on the canvas
}
I have the following code to do so:
img = new Image();
img.src = document.getElementById("input").value;
img.onload = function(){
console.log("loaded");
c.height = img.height;
c.width = img.width;
dimensions =[img.width,img.height];
ctx.drawImage(img,0,0,img.width,img.height);
imageData = ctx.getImageData(0,0,img.width,img.height).data;
ctx.clearRect(0,0,c.width,c.height);
};
However, on google chrome it throws the error Uncaught SecurityError: Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The canvas has been tainted by cross-origin data.
Not only that, it's a very complex way of doing a simple action. Any better ways of doing this? If not, help with the error?
What are you trying to do with the data? Depending on that you could possible use the FileReader.readAsDataURL(), especially since you are trying to get the data for the whole image.
Some code:
var input = document.getElementById('file');
var ctx2 = document.getElementById('uploadcanvas').getContext('2d');
var img2 = new Image;
var canvas = document.getElementById('uploadcanvas');
var imgprop = document.createElement("img");
var reader = new FileReader();
ctx2.save();
reader.onloadend = function(e){
imgprop.src = e.target.result
imgprop.onload = function(){
ctx2.restore();
URL.revokeObjectURL(img2.src);
ctx2.clearRect(0, 0, 100,100);
var width = imgprop.width;
var height = imgprop.height;
console.log(width, height);
canvas.width = width;
canvas.height = height;
img2.src = URL.createObjectURL(input.files[0]);
img2.onload = function() {
$('#display-image').css('display', "inline");
ctx2.drawImage(img2, 0, 0);
//URL.revokeObjectURL(img2.src);
};
$("#button").removeAttr("disabled");
$("#button").html("Upload to Facebook");
}
};
reader.readAsDataURL(input.files[0]);
function dataURItoBlob(dataURI) {
var byteString = atob(dataURI.split(',')[1]);
var ab = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(ab);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return new Blob([ab], {
type: 'image/png'
});
}