本文介绍了HTML 将 WebGL 画布另存为图像的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着跟版网的小编来一起学习吧！
问题描述
我正在使用 https://github.com/auduno/clmtrackr
我正在尝试从以下示例中获取要保存的图像:https://github.com/auduno/clmtrackr/blob/dev/examples/facedeform.html
I am trying to get the image to be saved from the following example: https://github.com/auduno/clmtrackr/blob/dev/examples/facedeform.html
问题是我显然已经尝试过canvas.dataToURL()".我可以将网络摄像头的视频作为图像获取；但是，叠加图像始终是透明的.
The issue is that I have obviously tried "canvas.dataToURL()". I can get the video of the webcam as an image; however, the overlay image is always transparent.
我尝试使用纹理在画布上绘制，但也没有用......
I attempted using the texture to draw on a canvas, but that also didn't work....
我这里有一个例子:https://codepen.io/msj121/pen/RgXjYK
我想将带有叠加层的整个图像保存到 png 中，比如我想的dataToURL".
I want to save the whole image with overlay to a png, like "dataToURL" I suppose.
// when everything is ready, automatically start everything ?
var vid = document.getElementById('videoel');
var vid_width = vid.width;
var vid_height = vid.height;
var overlay = document.getElementById('overlay');
var overlayCC = overlay.getContext('2d');
var webgl_overlay = document.getElementById('webgl');
// canvas for copying videoframes to
var videocanvas = document.createElement('CANVAS');
videocanvas.width = vid_width;
videocanvas.height = vid_height;
/*********** Setup of video/webcam and checking for webGL support *********/
var videoReady = false;
var imagesReady = false;
function enablestart() {
if (videoReady && imagesReady) {
var startbutton = document.getElementById('startbutton');
startbutton.value = "start";
startbutton.disabled = null;
}
}
$(window).load(function() {
imagesReady = true;
enablestart();
});
var insertAltVideo = function(video) {
if (supports_video()) {
if (supports_webm_video()) {
video.src = "./media/cap13_edit2.webm";
} else if (supports_h264_baseline_video()) {
video.src = "./media/cap13_edit2.mp4";
} else {
return false;
}
fd.init(webgl_overlay);
return true;
} else return false;
}
// check whether browser supports webGL
var webGLContext;
var webGLTestCanvas = document.createElement('canvas');
if (window.WebGLRenderingContext) {
webGLContext = webGLTestCanvas.getContext('webgl') || webGLTestCanvas.getContext('experimental-webgl');
if (!webGLContext || !webGLContext.getExtension('OES_texture_float')) {
webGLContext = null;
}
}
if (webGLContext == null) {
alert("Your browser does not seem to support WebGL. Unfortunately this face mask example depends on WebGL, so you'll have to try it in another browser. :(");
}
function gumSuccess( stream ) {
// add camera stream if getUserMedia succeeded
if ("srcObject" in vid) {
vid.srcObject = stream;
} else {
vid.src = (window.URL && window.URL.createObjectURL(stream));
}
vid.onloadedmetadata = function() {
// resize overlay and video if proportions are different
var proportion = vid.videoWidth/vid.videoHeight;
vid_width = Math.round(vid_height * proportion);
vid.width = vid_width;
overlay.width = vid_width;
webgl_overlay.width = vid_width;
videocanvas.width = vid_width;
fd.init(webgl_overlay);
vid.play();
}
}
function gumFail() {
// fall back to video if getUserMedia failed
insertAltVideo(vid);
alert("There was some problem trying to fetch video from your webcam, using a fallback video instead.");
}
navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;
window.URL = window.URL || window.webkitURL || window.msURL || window.mozURL;
// check for camerasupport
if (navigator.mediaDevices) {
navigator.mediaDevices.getUserMedia({video : true}).then(gumSuccess).catch(gumFail);
} else if (navigator.getUserMedia) {
navigator.getUserMedia({video : true}, gumSuccess, gumFail);
} else {
insertAltVideo(vid);
alert("Your browser does not seem to support getUserMedia, using a fallback video instead.");
}
vid.addEventListener('canplay', function() {videoReady = true;enablestart();}, false);
/*********** Code for face substitution *********/
var animationRequest;
var positions;
var ctrack = new clm.tracker();
ctrack.init(pModel);
function startVideo() {
// start video
vid.play();
// start tracking
ctrack.start(vid);
// start drawing face grid
drawGridLoop();
}
var fd = new faceDeformer();
var mouth_vertices = [
[44,45,61,44],
[45,46,61,45],
[46,60,61,46],
[46,47,60,46],
[47,48,60,47],
[48,59,60,48],
[48,49,59,48],
[49,50,59,49],
[50,51,58,50],
[51,52,58,51],
[52,57,58,52],
[52,53,57,52],
[53,54,57,53],
[54,56,57,54],
[54,55,56,54],
[55,44,56,55],
[44,61,56,44],
[61,60,56,61],
[56,57,60,56],
[57,59,60,57],
[57,58,59,57],
[50,58,59,50],
];
var extendVertices = [
[0,71,72,0],
[0,72,1,0],
[1,72,73,1],
[1,73,2,1],
[2,73,74,2],
[2,74,3,2],
[3,74,75,3],
[3,75,4,3],
[4,75,76,4],
[4,76,5,4],
[5,76,77,5],
[5,77,6,5],
[6,77,78,6],
[6,78,7,6],
[7,78,79,7],
[7,79,8,7],
[8,79,80,8],
[8,80,9,8],
[9,80,81,9],
[9,81,10,9],
[10,81,82,10],
[10,82,11,10],
[11,82,83,11],
[11,83,12,11],
[12,83,84,12],
[12,84,13,12],
[13,84,85,13],
[13,85,14,13],
[14,85,86,14],
[14,86,15,14],
[15,86,87,15],
[15,87,16,15],
[16,87,88,16],
[16,88,17,16],
[17,88,89,17],
[17,89,18,17],
[18,89,93,18],
[18,93,22,18],
[22,93,21,22],
[93,92,21,93],
[21,92,20,21],
[92,91,20,92],
[20,91,19,20],
[91,90,19,91],
[19,90,71,19],
[19,71,0,19]
]
function drawGridLoop() {
// get position of face
positions = ctrack.getCurrentPosition();
overlayCC.clearRect(0, 0, vid_width, vid_height);
if (positions) {
// draw current grid
ctrack.draw(overlay);
}
// check whether mask has converged
var pn = ctrack.getConvergence();
if (pn < 0.4) {
drawMaskLoop();
} else {
requestAnimFrame(drawGridLoop);
}
}
function drawMaskLoop() {
videocanvas.getContext('2d').drawImage(vid,0,0,videocanvas.width,videocanvas.height);
var pos = ctrack.getCurrentPosition();
if (pos) {
// create additional points around face
var tempPos;
var addPos = [];
for (var i = 0;i < 23;i++) {
tempPos = [];
tempPos[0] = (pos[i][0] - pos[62][0])*1.3 + pos[62][0];
tempPos[1] = (pos[i][1] - pos[62][1])*1.3 + pos[62][1];
addPos.push(tempPos);
}
// merge with pos
var newPos = pos.concat(addPos);
var newVertices = pModel.path.vertices.concat(mouth_vertices);
// merge with newVertices
newVertices = newVertices.concat(extendVertices);
fd.load(videocanvas, newPos, pModel, newVertices);
var parameters = ctrack.getCurrentParameters();
for (var i = 6;i < parameters.length;i++) {
parameters[i] += ph['component '+(i-3)];
}
positions = ctrack.calculatePositions(parameters);
overlayCC.clearRect(0, 0, vid_width, vid_height);
if (positions) {
// add positions from extended boundary, unmodified
newPos = positions.concat(addPos);
// draw mask on top of face
fd.draw(newPos);
}
}
animationRequest = requestAnimFrame(drawMaskLoop);
}
/*********** Code for stats **********/
stats = new Stats();
stats.domElement.style.position = 'absolute';
stats.domElement.style.top = '0px';
document.getElementById('container').appendChild( stats.domElement );
document.addEventListener("clmtrackrIteration", function(event) {
stats.update();
}, false);
/********** parameter code *********/
var pnums = pModel.shapeModel.eigenValues.length-2;
var parameterHolder = function() {
for (var i = 0;i < pnums;i++) {
this['component '+(i+3)] = 0;
}
this.presets = 0;
};
var ph = new parameterHolder();
var gui = new dat.GUI();
var presets = {
"unwell" : [0, 0, 0, 0, 0, 0, 22, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
"inca" : [0, 0, -9, 0, -11, 0, 0, 0, 0, 0, 0, 0, 12, 0, 0, 0, 0, 0],
"cheery" : [0, 0, -9, 9, -11, 0, 0, 0, 0, 0, 0, 0, -9, 0, 0, 0, 0, 0],
"dopey" : [0, 0, 0, 0, 0, 0, 0, -11, 0, 0, 0, 0, 0, 0, 20, 0, 0, 0],
"longface" : [0, 0, 0, 0, -15, 0, 0, -12, 0, 0, 0, 0, 0, 0, -7, 0, 0, 5],
"lucky" : [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -4, 0, -6, 12, 0, 0],
"overcute" : [0, 0, 0, 0, 16, 0, -14, 0, 0, 0, 0, 0, -7, 0, 0, 0, 0, 0],
"aloof" : [0, 0, 0, 0, 0, 0, 0, -8, 0, 0, 0, 0, 0, 0, -2, 0, 0, 10],
"evil" : [0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, -8],
"artificial" : [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 11, 0, -16, 0, 0, 0, 0, 0],
"none" : [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
};
var control = {};
var eig = 0;
for (var i = 0;i < pnums;i++) {
eig = Math.sqrt(pModel.shapeModel.eigenValues[i+2])*3
control['c'+(i+3)] = gui.add(ph, 'component '+(i+3), -5*eig, 5*eig).listen();
}
/********** defaults code **********/
function switchDeformedFace(e) {
//var split = ph.presets.split(",");
for (var i = 0;i < pnums;i++) {
ph['component '+(i+3)] = presets[e.target.value][i];
}
}
document.getElementById('deform').addEventListener('change', switchDeformedFace, false);
for (var i = 0;i < pnums;i++) {
ph['component '+(i+3)] = presets['unwell'][i];
}
推荐答案
stackoverflow 上已经回答了至少 10 次 webgl 画布为空白的原因
The reason the webgl canvas is blank has been answered at least 10 times here on stackoverflow
通过 canvas.toDataURL 将画布保存到图像会导致黑色矩形
Canvas toDataURL() 仅在 Firefox 中返回空白图像
toDataURL()的webgl画布返回透明图片
为什么我的画布在转换为图片?
我知道还有几个，但我懒得搜索所有这些
I know there's several more but I'm too lazy to search for all of them
我没有将此标记为重复的唯一原因是因为您想要 2 个画布中的 1 个 png.
The only reason I didn't mark this as a duplicate is because you wanted 1 png from 2 canvases.
如果您只想要 1 个 png，那么您需要从一个画布上捕获.因此，将 WebGL 画布绘制到视频画布中，然后在视频画布上调用 toDataURL.
If you want just 1 png then you need to capture from one canvas. So, draw the WebGL canvas into the video canvas then call toDataURL on the video canvas.
const vctx = videocanvas.getContext('2d');
vctx.drawImage(webGLTestCanvas, 0, 0);
const capturedImage = videocanvas.toDataURL();
这篇关于HTML 将 WebGL 画布另存为图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！
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