canvas

Speed up adding objects to Canvas In WPF

由 故事扮演 提交于 2019-12-28 03:04:29
问题 I have a Canvas that I am using in WPF to draw many colored rectangles to but the program is running really slow when they are being added. I have tried different options, such as adding them to an Array and adding them all at once and using a Image instead of a Canvas to dispay them, but they didn't seem to do much. I have the coding leading up the drawing in a thread, but because of C# rules, I have to have the drawing part in the main thread. I should also note that the problem isn't my

Speed up adding objects to Canvas In WPF

由 ε祈祈猫儿з 提交于 2019-12-28 03:04:06
问题 I have a Canvas that I am using in WPF to draw many colored rectangles to but the program is running really slow when they are being added. I have tried different options, such as adding them to an Array and adding them all at once and using a Image instead of a Canvas to dispay them, but they didn't seem to do much. I have the coding leading up the drawing in a thread, but because of C# rules, I have to have the drawing part in the main thread. I should also note that the problem isn't my

vue使用qrcodejs2生成二维码图片

由 折月煮酒 提交于 2019-12-27 20:56:41
根据url路径生成一张二维码图片。 1.下载相关依赖 npm install qrcodejs2 --save 2.相关组件引入 import QRCode from 'qrcodejs2' 3.html <div id='qrcode'></div> 4.js 在需要的地方进行调用，一般是后台返回链接之后进行调用 new QRCode('qrcode',{ width:'6rem', height:'6rem', text:'此处放生成二维码的地址', colorDark:'#000',//二维码颜色 colorLight:'#fff',//二维码背景色 // correctLevel: QRCode.CorrectLevel.L//容错率，L/M/H //render: 'canvas' // 设置渲染方式（有两种方式 table和canvas，默认是canvas） }) 来源： CSDN 作者： s先生的d小姐 链接： https://blog.csdn.net/weixin_44326389/article/details/103734248

Drawing text to <canvas> with @font-face does not work at the first time

由 元气小坏坏 提交于 2019-12-27 11:11:40
问题 When I draw a text in a canvas with a typeface that is loaded via @font-face, the text doesn't show correctly. It doesn't show at all (in Chrome 13 and Firefox 5), or the typeface is wrong (Opera 11). This type of unexpected behavior occurs only at the first drawing with the typeface. After then everything works fine. Is it the standard behavior or something? Thank you. PS: Following is the source code of the test case <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>@font-face and

Drawing text to <canvas> with @font-face does not work at the first time

由 回眸只為那壹抹淺笑 提交于 2019-12-27 11:10:13
问题 When I draw a text in a canvas with a typeface that is loaded via @font-face, the text doesn't show correctly. It doesn't show at all (in Chrome 13 and Firefox 5), or the typeface is wrong (Opera 11). This type of unexpected behavior occurs only at the first drawing with the typeface. After then everything works fine. Is it the standard behavior or something? Thank you. PS: Following is the source code of the test case <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>@font-face and

Canvas image crossplatform insecure error

由 和自甴很熟 提交于 2019-12-27 10:30:27
问题 I have this code for create canvas image from different server urls function getBase64Image(imageUri) { var canvas = document.createElement("canvas"); ctx = canvas.getContext("2d"); var img = new Image(); img.src = imageUri; img.crossOrigin = "Anonymous"; img.onload = function() { canvas.width = this.width; canvas.height = this.height; ctx.drawImage(img, 0, 0, this.width, this.height); var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height); var dataURL = canvas.toDataURL("image

Canvas image crossplatform insecure error

由 ￣綄美尐妖づ 提交于 2019-12-27 10:29:32
问题 I have this code for create canvas image from different server urls function getBase64Image(imageUri) { var canvas = document.createElement("canvas"); ctx = canvas.getContext("2d"); var img = new Image(); img.src = imageUri; img.crossOrigin = "Anonymous"; img.onload = function() { canvas.width = this.width; canvas.height = this.height; ctx.drawImage(img, 0, 0, this.width, this.height); var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height); var dataURL = canvas.toDataURL("image

android canvas中rotate()和translate()两个方法详解

由 血红的双手。 提交于 2019-12-27 09:19:15
rotate()和translate() 1.看到这个题目的时候，有人会觉得这不就是一个对画布的旋转和平移的嘛，但是其中的细节的地方还是需要深究一下的。 例如: 有个需求将TextView的文字竖直显示 。 　　首先想到的方法就是将画布旋转90度，代码如下： 1 public class RotateTextView extends TextView { 2 public RotateTextView(Context context) { 3 super(context); 4 } 5 6 public RotateTextView(Context context, AttributeSet attrs) { 7 super(context, attrs); 8 } 9 10 public RotateTextView(Context context, AttributeSet attrs, int defStyle) { 11 super(context, attrs, defStyle); 12 } 13 14 @Override 15 protected void onDraw(Canvas canvas) { 16 canvas.rotate(90); 17 super.onDraw(canvas); 18 } 19 20 } 在利用这个自定义的View 1

微信小程序分享朋友圈的实现思路与解决办法

由 独自空忆成欢 提交于 2019-12-26 19:05:28
简介 截止我写这篇文章的时候，小程序应该是还没有能够直接分享到朋友圈的api,转发给朋友和群是可以实现的，这篇文章主要是讲如何实现分享到朋友圈。 实现思路 那么既然小程序没有分享到朋友圈的api,我们怎么实现分享到朋友圈呢，下面我介绍一下实现思路。 既然没有捷径，那就走复杂一点的路线，那就是需要用户手动分享到朋友圈，问题又来了，用户手动分享的话，分享什么呢？我们其实在朋友圈应该已经看到不少带有小程序码的图片，特别是年前与年后，应该看到不少智行火车票，携程火车票分享到朋友圈的图片，帮助好友加速，用来抢火车票，还有像今日头条，分享新闻到朋友圈的方式。 他们共同的策略是生成一张带有小程序码的图片，小程序码包含了分享者的用户信息，我们把图片生成以后，用户自行保存图片到本地，然后分享到朋友圈，朋友圈好友长按图片识别图中二维码，进入小程序后解析小程序码携带的信息，生成相应的页面。这样就实现了分享到朋友圈这样一个流程。 在这个流程中有两个难点。 第一个难点是怎么生成带有小程序码的图片，因为生成的图片通常都不是孤零零的只有小程序码，而且注意我们是要“生成一张图片保存到本地“。 第二个难点是生成图片了，分享到朋友圈了，好友通过我们分享的小程序码进入小程序了，那么我们怎么提取小程序码携带的用户信息，获取其中携带的参数？ 生成图片 目前我所知道的有两种方式生成小程序分享图片，第一种是前端生成

【Java】JavaWeb文件上传和下载

由 妖精的绣舞 提交于 2019-12-26 03:12:10
　　web网站中常常有的功能：上传头像、上传封面等；一般图片都有一定的比例限制，所以需要前端在上传图片时，进行裁剪，并把裁剪后的图片进行上传。 　　本例采用Jcrop插件实现裁剪效果，canvas裁剪图片，并把base64位的toDataURL图片转换成blob（二进制数据），最后使用XMLHttpRequest上传到服务器。 　　Jcrop演示及下载地址： http://code.ciaoca.com/jquery/jcrop/demo/ Jcrop的使用 　　本例做Jcrop的简单预览功能（同理可以实现网页的放大镜功能） 载入 CSS 文件 1 <link rel="stylesheet" href="jquery.Jcrop.css"> 载入 JavaScript 文件 1 <script src="jquery.js"></script> 2 <script src="jquery.Jcrop.js"></script> 给 IMG 标签加上 ID 1 <img id="element_id" src="pic.jpg"> 调用 Jcrop 1 $('#element_id').Jcrop(); 实例代码 1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4 <meta charset="UTF-8"> 5 <title>图像裁剪
订阅 canvas