透過網頁讀取PSD後，依圖層輸出PNG檔案

by 馬老師 · 2020-04-30

在前面介紹過網頁可以讀取PSD檔案並擷取到該檔案的資訊，接著我們會希望能透過網頁上傳PSD檔之後，依照圖層來輸出圖片，同樣是利用PSD.js來輔助進行，可以透過我們製作的範例頁面來進行輸出測試。

預設輸出效果

透過PSD.js可將PSD內的各圖層輸出成PNG圖檔，亦可轉成Base 64圖檔格式，惟輸出時每個圖檔的尺寸並不會根據整體PSD檔大小來配置。

Layer 1 (421 x 38)

<!DOCTYPE html>
<html>
<head>
  <title>psd.js image example</title>
  <style type="text/css">
  body, html {
    padding: 0;
    margin: 0;
  }

  #dropzone {
    width: 500px;
    height: 100px;
    border: 1px #ababab dashed;
    margin: 50px auto;
  }

  #dropzone p {
    text-align: center;
    line-height: 100px;
    margin: 0;
    padding: 0;
  }

  #image {
    text-align: center;
  }
  </style>

  <script type="text/javascript" src="psd.min.js"></script>
</head>
<body>
  <div id="dropzone">
    <p>Drop PSD here</p>
  </div>
  <div id="image"></div>
  <pre id="data"></pre>

  <script type="text/javascript">
  (function () {
    const PSD = require('psd');

    document.getElementById('dropzone').addEventListener('dragover', onDragOver, true);
    document.getElementById('dropzone').addEventListener('drop', onDrop, true);

    function onDragOver(e) {
      e.stopPropagation();
      e.preventDefault();
      e.dataTransfer.dropEffect = 'copy';
    }

    function onDrop(e) {
      e.stopPropagation();
      e.preventDefault();
      PSD.fromEvent(e).then(function (psd) {
		for (var i = 0; i < psd.layers.length; i ++){
			document.getElementById('image').appendChild(psd.layers[i].image.toPng());
		}
      });
    }
	
  }());
  </script>
</body>
</html>

依照整體PSD配置進行輸出

我們希望讓每個圖片在輸出後能保時相同的尺寸，也就是依照PSD的畫布大小來輸出每一張圖檔，但在原生PSD.js中並不具備這樣的功能，於是我們透過下述的方式來達成：

擷取PSD資訊並將圖檔轉為Base 64格式
產生與PSD尺寸大小相同的HTML Canvas
將產生的Base 64圖檔，依照原始位置放入Canvas中
將Canvas轉成PNG圖檔

可以參考我們製作的範例頁面

<!DOCTYPE html>
<html>
<head>
  <title>psd.js image example</title>
  <style type="text/css">
  body, html {
    padding: 0;
    margin: 0;
  }
  #dropzone {
    width: 500px;
    height: 100px;
    border: 1px #ababab dashed;
    margin: 50px auto;
  }
  #dropzone p {
    text-align: center;
    line-height: 100px;
    margin: 0;
    padding: 0;
  }
  #image {
    text-align: center;
  }
  </style>
  <script type="text/javascript" src="psd.min.js"></script>
</head>
<body>
  <div id="dropzone">
    <p>Drop PSD here</p>
  </div>
  <div id="image"></div>
  <pre id="data"></pre>
  <script type="text/javascript">
  (function () {
    const PSD = require('psd');
    document.getElementById('dropzone').addEventListener('dragover', onDragOver, true);
    document.getElementById('dropzone').addEventListener('drop', onDrop, true);
    function onDragOver(e) {
      e.stopPropagation();
      e.preventDefault();
      e.dataTransfer.dropEffect = 'copy';
    }
    function onDrop(e) {
      e.stopPropagation();
      e.preventDefault();
      PSD.fromEvent(e).then(function (psd) {
    const PSDWidth = psd.tree().width;
    const PSDHeight = psd.tree().height;
    for (var i = 0; i < psd.layers.length; i ++){
      const img = new Image();
      img.src = psd.layers[i].image.toBase64();
      console.log(psd);
      const layerWidth = psd.layers[i].width;
      const layerHeight = psd.layers[i].height;
      const layerLeft = psd.layers[i].left;
      const layerTop = psd.layers[i].top;
      
      const canvas = document.createElement("canvas");
      canvas.setAttribute('class', "canvas");
      canvas.width = PSDWidth;
      canvas.height = PSDHeight;
      console.log("canvas :", canvas);
      img.onload = function(){
        canvas.getContext("2d").drawImage(img, layerLeft, layerTop, layerWidth, layerHeight);
        document.getElementById('image').appendChild(canvas);
      }
    }
      });
    }
  
  }());
  </script>
</body>
</html>