如何使用Dart将图像从剪贴板粘贴到Canvas元素？ [英] How can I paste an image from the clipboard onto a Canvas element using Dart?

问题描述

我使用Dart开发一个个人白板Chrome应用程式，有时能够快速复制和粘贴图像（例如，从演示文稿，图表或讲义中的幻灯片），以便我可以添加笔记

I'm using Dart to develop a personal whiteboard Chrome app and it is sometimes useful to be able to quickly copy and paste an image (e.g. a slide from a presentation, a diagram or a handout) so that I can add notes over the image while teaching a class or giving a presentation.

如何将存储在剪贴板上的图片粘贴到Dart中的canvas元素上？

How can I paste an image stored on the clipboard onto a canvas element in Dart?

推荐答案

实际上，这个问题对于JS 几乎可以直接应用。 Dart翻译可能如下所示：

Actually, this answer to the same question for JS is almost directly applicable. A Dart translation might look something like:

import 'dart:html';

void main() {
  var can = new CanvasElement()
    ..width = 600
    ..height = 600
  ;

  var con = can.getContext('2d');

  document.onPaste.listen((e) {
    var blob = e.clipboardData.items[0].getAsFile();
    var reader = new FileReader();
    reader.onLoad.listen((e) {
      var img = new ImageElement()
        ..src = (e.target as FileReader).result;
      img.onLoad.listen((_) {
        con.drawImage(img, 0, 0);
      });
    });
    reader.readAsDataUrl(blob);
  });

  document.body.children.add(can);
}

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