var canvasImage = canvas.toDataURL("image/png");
var blob = {
  mainFile: canvasImage,
  filename: this.file.name + '_edited',
  isWriteable: true,
  };

postFile(blob) {
      var _this = this;
      this.filepickerService.store(blob,
        {
          mimetype: "text/plain",
          location: "S3",
          path: "muhPath"
          container: _this.appConfig.s3Bucket
        },
        function(new_blob){
          console.log(JSON.stringify(new_blob));
        }
      );
  }

Cannot store given input: " + input + ". Not a string, file input, DOM File, or FPFile object.