情况
我有144个(90px x 90px)图像(12x12)可以旋转的网格状无序列表。我的最终目标是拍摄144个图像网格并将其另存为1个图像。
当前解决方案
我当前的解决方案是按照以下步骤操作:
注意事项
当我遍历图像时,我会跟踪一个指针(我当前在 Canvas 上的位置)。我通过保持一行和一个列号来做到这一点。它们代表了我正在绘制的图像的当前行和列。我用它们乘以单个图像的宽度和高度来获得 Canvas 上确切的x和y坐标以绘制下一个图像。
当前问题
当我调用该函数来创建,绘制和生成 Canvas 的base64时,会收到以下错误消息:“InvalidStateError:试图使用一个不可用或不再可用的对象。”。如果此错误发生的可能性为100%,则我将其假定为是因为我要绘制到 Canvas 上的图像尚未加载或根本没有加载,但是,我只收到一次此错误,原因是我加载的每个新图像。例如,如果我有一个144个图像网格,即2个不同的图像,每个图像绘制72次,则我将两次收到InvalidStateError,然后第三次调用该函数,它将成功。
当前代码
请记住,这只是用于测试保存图像的秒杀代码,我知道需要一些重构。
generateThumbnail: function(){
var builder = this,
canvas = document.createElement('canvas'),
content,
row = 0,
col = 0;
// width is single image width (90) x number of tiles wide (usually 12)
canvas.width = 90 * builder.grid[0];
// height is single image height (90) x number of tiles high (usually 12)
canvas.height = 90 * builder.grid[1];
// get 2d context of new canvas
context = canvas.getContext("2d");
// loop through all of the images on the grid
$.each($(".pattern-grid li"), function(i, tile) {
var $tile = $(tile),
image = new Image(),
src = $tile.find("img").attr("src"),
width,
height,
buffer,
bufferctx,
x,
y;
// set crossOrigin of image to anonymous as these images are loaded via CORS
image.crossOrigin = "Anonymous";
// increase row number by 1 if it has reached the end of the row and its not the first image being drawn
if(i % builder.grid[0] == 0 && i != 0){
row++;
}
// Set Column to 0 if it is a new row, otherwise increase column by 1 (unless it is the first image being drawn)
if(col == builder.grid[0]-1){
col = 0;
}else if(i != 0){
col++;
}
// determine if there was no image drawn at this location
if(src != undefined){
image.src = src;
// get the width and height the image, to be used for the small canvas and where to draw it
width = image.width;
height = image.height;
// create a new buffer canvas to draw the image to, this will be used to apply any rotations that may exist
buffer = document.createElement("canvas");
//set width and height of the buffer to the current images width and height
buffer.width = width;
buffer.height = height;
bufferctx = buffer.getContext("2d");
//Determine x and y coordinates to draw the small canvas using row and column numbers
x = col*width;
y = row*height;
//Save current state of buffer canvas
bufferctx.save();
//translate and then rotate the buffer canvas by the image's rotation
bufferctx.translate(width/2, height/2);
bufferctx.rotate($tile.find("img").data("rotation")*Math.PI/180);
bufferctx.translate(width/2*-1, height/2*-1);
//draw image to buffer canvas and restore its context
bufferctx.drawImage(image, 0, 0);
bufferctx.restore();
//draw the buffer canvas to the main canvas at predetermined x and y
context.drawImage(buffer, x, y, width, height);
}
});
return canvas.toDataURL();
}
最佳答案
我可以将@abiessu的建议与onload一起使用,并与闭包配对以保存函数的状态。我有效的解决方案是:
generateThumbnail: function(){
var builder = this,
canvas = document.createElement('canvas'),
content,
row = 0,
col = 0;
// width is single image width (90) x number of tiles wide (usually 12)
canvas.width = 90 * builder.grid[0];
// height is single image height (90) x number of tiles high (usually 12)
canvas.height = 90 * builder.grid[1];
context = canvas.getContext("2d");
// loop through all of the images on the grid
$.each($(".pattern-grid li"), function(i, tile) {
var $tile = $(tile),
image = new Image(),
src = $tile.find("img").attr("src");
// set crossOrigin of image to anonymous as these images are loaded via CORS
image.crossOrigin = "Anonymous";
// increase row number by 1 if it has reached the end of the row and its not the first image being drawn
if(i % builder.grid[0] == 0 && i != 0){
row++;
}
// increase row number by 1 if it has reached the end of the row and its not the first image being drawn
if(col == builder.grid[0]-1){
col = 0;
}else if(i != 0){
col++;
}
image.onload = function(row, col){
return function(){
// determine if there was no image drawn at this location
if(src != undefined){
var width = image.width,
height = image.height,
buffer = document.createElement("canvas"),
bufferctx,
x,
y;
buffer.width = width;
buffer.height = height;
bufferctx = buffer.getContext("2d");
x = col*width;
y = row*height;
bufferctx.save();
bufferctx.translate(width/2, height/2);
bufferctx.rotate($tile.find("img").data("rotation")*Math.PI/180);
bufferctx.translate(width/2*-1, height/2*-1);
bufferctx.drawImage(image, 0, 0);
bufferctx.restore();
context.drawImage(buffer, x, y, width, height);
}
}
}(row, col);
image.src = $tile.find("img").attr("src");
});
window.canvas = canvas;
}