将画布保存为png，在html/javascript Air应用程序中没有提示

Save canvas as png without prompt in html/javascript Air app

本文关键字：Air javascript html 应用程序提示布保存保存 png 更新时间：2023-09-26

我使用html2canvas来创建应用程序的一个部分的屏幕截图。我确实有工作代码，但它提示用户保存。我希望png保存不提示。

这是我的工作代码(但有用户提示):

html2canvas( $('#renderCover'), {
      onrendered: function(canvas) {
          var base64ToByteArray = function(encStr){
            var base64s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
             var decOut = new air.ByteArray();  
            var bits;
            for(var i = 0, j = 0; i<encStr.length; i += 4, j += 3){
                bits = (base64s.indexOf(encStr.charAt(i)) & 0xff) <<18 | (base64s.indexOf(encStr.charAt(i +1)) & 0xff) <<12 | (base64s.indexOf(encStr.charAt(i +2)) & 0xff) << 6 | base64s.indexOf(encStr.charAt(i +3)) & 0xff;
                decOut[j+0] = ((bits & 0xff0000) >> 16);
                  if(i+4 != encStr.length || encStr.charCodeAt(encStr.length - 2) != 61){
                       decOut[j+1] = ((bits & 0xff00) >> 8);
                  }
                  if(i+4 != encStr.length || encStr.charCodeAt(encStr.length - 1) != 61){
                       decOut[j+2] = (bits & 0xff);
                  }
            }
            return decOut;
        };
        var dataURL = canvas.toDataURL("image/png");
        dataURL = dataURL.replace(/^data:image'/(png|jpg);base64,/, "");
        dataURL = base64ToByteArray(dataURL);
        var file = air.File.documentsDirectory.resolvePath("Air Test/testPNG.png"); 
        file.save(dataURL); 
      }
    });

这是我的尝试没有提示，但我得到错误，类型强制转换失败:

html2canvas( $('#renderCover'), {
      onrendered: function(canvas) {
          var base64ToByteArray = function(encStr){
            var base64s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
             var decOut = new air.ByteArray();  
            var bits;
            for(var i = 0, j = 0; i<encStr.length; i += 4, j += 3){
                bits = (base64s.indexOf(encStr.charAt(i)) & 0xff) <<18 | (base64s.indexOf(encStr.charAt(i +1)) & 0xff) <<12 | (base64s.indexOf(encStr.charAt(i +2)) & 0xff) << 6 | base64s.indexOf(encStr.charAt(i +3)) & 0xff;
                decOut[j+0] = ((bits & 0xff0000) >> 16);
                  if(i+4 != encStr.length || encStr.charCodeAt(encStr.length - 2) != 61){
                       decOut[j+1] = ((bits & 0xff00) >> 8);
                  }
                  if(i+4 != encStr.length || encStr.charCodeAt(encStr.length - 1) != 61){
                       decOut[j+2] = (bits & 0xff);
                  }
            }
            return decOut;
        };
        var dataURL = canvas.toDataURL("image/png");
        dataURL = dataURL.replace(/^data:image'/(png|jpg);base64,/, "");
        dataURL = base64ToByteArray(dataURL);
        var storage = 'documentsDirectory';
        var localFile = air.File[storage].resolvePath( "Air Test/testPNG.png" );
        var stream = new air.URLStream();
        stream.addEventListener(air.Event.COMPLETE, function(e){
            var fileData = new air.ByteArray();
            stream.readBytes(fileData,0,stream.bytesAvailable);
            var fileStream = new air.FileStream();
            fileStream.openAsync(localFile, air.FileMode.WRITE);
            fileStream.writeBytes(fileData,0);
            fileStream.close();
        });
        stream.load(dataURL);

      }
    });

有没有办法将画布保存为png本地没有用户提示?

谢谢，不过我自己修好了。下面是在不需要用户提示的情况下将画布保存为.png的工作代码:

html2canvas( $('#renderCover'), {
      onrendered: function(canvas) {
        var base64ToByteArray = function(encStr){
            var base64s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
            var decOut = new air.ByteArray();  
            var bits;
            for(var i = 0, j = 0; i<encStr.length; i += 4, j += 3){
                bits = (base64s.indexOf(encStr.charAt(i)) & 0xff) <<18 | (base64s.indexOf(encStr.charAt(i +1)) & 0xff) <<12 | (base64s.indexOf(encStr.charAt(i +2)) & 0xff) << 6 | base64s.indexOf(encStr.charAt(i +3)) & 0xff;
                decOut[j+0] = ((bits & 0xff0000) >> 16);
                  if(i+4 != encStr.length || encStr.charCodeAt(encStr.length - 2) != 61){
                       decOut[j+1] = ((bits & 0xff00) >> 8);
                  }
                  if(i+4 != encStr.length || encStr.charCodeAt(encStr.length - 1) != 61){
                       decOut[j+2] = (bits & 0xff);
                  }
            }
            return decOut;
        };
        var dataURL = canvas.toDataURL("image/png");
        dataURL = dataURL.replace(/^data:image'/(png|jpg);base64,/, "");
        dataURL = base64ToByteArray(dataURL);
        var storage = 'documentsDirectory';
        var localFile = air.File[storage].resolvePath( "Air Test/testPNG.png" );
        var stream = new air.FileStream();
        stream.open(localFile, air.FileMode.WRITE);
        stream.writeBytes(dataURL,0);
        stream.close();
      }
});