一.帶隱藏文字資訊的圖片

通過RGB 分量值的小量變動，不影響對圖片的識別。因此，我們可以在圖片加入文字資訊。

最終達到如下效果:

首先，在該元件中加入img用於顯示圖片

<canvas ref="canvas" v-show="0"></canvas>
<img :src="imageUrl" v-if="imageUrl"/>

呼叫方法

encryptionImg({
    width = '',height = '',content = '',}){
    let img = this.img
    const imgRatio = img.naturalWidth / img.naturalHeight;
    const ctxWidth = width || img.naturalWidth;
    const ctxHeight = height || ctxWidth / imgRatio;
    this.canvas.width = ctxWidth;
    this.canvas.height = ctxHeight;
    const ctx = this.ctx;
    ctx.font = '16px Microsoft Yahei';
    ctx.textAlign = 'left';
    ctx.textBaseline = 'top';
    ctx.fillText(content,12,ctxHeight/2,ctxWidth);17     const textData = ctx.getImageData(0,ctxWidth,ctxHeight);
    this.imageUrl = this.mergeData(textData.data,'R',ctxHeight);19    }

把文字和圖片整合成一張圖

mergeData(newData,color,width,height) {
    let img = this.img
    this.ctx.drawImage(img,height);
    this.originalData = this.ctx.getImageData(0,height);
    var oData = this.originalData.data;
    var bit,offset;
    switch (color) {
     case 'R':
      bit = 0;
      offset = 3;
      break;
     case 'G':
      bit = 1;
      offset = 2;
      break;
     case 'B':
      bit = 2;
      offset = 1;
      break;
    }
    for (var i = 0; i < oData.length; i++) {
     if (i % 4 == bit) {
      if (newData[i + offset] === 0 && (oData[i] % 2 === 1)) {
       if (oData[i] === 255) {
        oData[i]--
       } else {
        oData[i]++
       }
      } else if (newData[i + offset] !== 0 && (oData[i] % 2 === 0)) {
       if (oData[i] === 255) {
        oData[i]--
       } else {
        oData[i]++
       }
      }
     }
    }
    this.ctx.putImageData(this.originalData,0);
    return this.canvas.toDataURL();
   },

呼叫下面方法，解開圖片資訊

decryptImg(){
    var data = this.originalData.data;
    for(var i = 0; i < data.length; i++){
     if(i % 4 == 0){
      if(data[i] % 2 == 0){
       data[i] = 0;
      } else {
       data[i] = 255;
      }
     } else if(i % 4 == 3){
      continue;
     } else {
      data[i] = 0;
     }
    }
    this.ctx.putImageData(this.originalData,0);
    this.imageUrl = this.canvas.toDataURL();
   },

二.圖片水印

watermark({
    content = '',container = '',width = '',position = 'bottom-right',font = '16px 微軟雅黑',fillStyle = 'rgba(255,255,1)',zIndex = 11000,} = {}) {
    let img = this.img
    const imgRatio = img.naturalWidth / img.naturalHeight;
    const ctxWidth = width || img.naturalWidth;
    const ctxHeight = height || ctxWidth / imgRatio;
    this.canvas.width = ctxWidth;
    this.canvas.height = ctxHeight;
    const ctx = this.ctx;
    ctx.drawImage(img,ctxHeight);
    ctx.shadowColor = 'rgba(0,0.2)';
    ctx.shadowOffsetX = 2;
    ctx.shadowOffsetY = 2;
    ctx.shadowBlur = 2;
    ctx.font = font;
    ctx.fillStyle = fillStyle;
    if(position == 'center') {
     ctx.textAlign = 'center';
     ctx.textBaseline = 'middle';
     ctx.fillText(content,ctxWidth / 2,ctxHeight / 2,ctxWidth)
    }else if(position == 'bottom-right') {
     ctx.textAlign = 'right';
     ctx.textBaseline = 'alphabetic';
     ctx.fillText(content,ctxWidth-12,ctxHeight-12,ctxWidth)
    }
    const base64Url = this.canvas.toDataURL();
    if(container) {
     const div = document.createElement('div');
     div.setAttribute('style',` width: ${ctxWidth}px; height: ${ctxHeight}px; z-index: ${zIndex}; 
     pointer-events: none; background-repeat: repeat; background-image: url('${base64Url}')`);
     container.insertBefore(div,null);
    }
    this.imageUrl = base64Url
   }

參考

http://www.alloyteam.com/2016/03/image-steganography/

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