Originally from https://github.com/maxlabelle/filepreview

filepreview.js

/*

  filepreview : A file preview generator for node.js

*/

var child_process = require('child_process');
var crypto = require('crypto');
var async = require('async');
var path = require('path');
var fs = require('fs');
var os = require('os');
var mimedb = require('./db.json');

module.exports = {
  generate: function(input_original, output, options, callback) {
    // Normalize arguments

    var input = input_original;

    if (typeof options === 'function') {
      callback = options;
      options = {};
    } else {
      options = options || {};
    }

    // Check for supported output format
    var extOutput = path.extname(output).toLowerCase().replace('.','');
    var extInput = path.extname(input).toLowerCase().replace('.','');

    if (
      extOutput != 'gif' &&
      extOutput != 'jpg' &&
      extOutput != 'png'
    ) {
      return callback(true);
    }

    var fileArgs = [input_original];
    var fileExecOutput = child_process.execFileSync('file', fileArgs);
    var is_executable = fileExecOutput.toString().indexOf("executable");
    if (parseInt(is_executable) > 0) {
      return callback(true);
    }

    var fileType = 'other';

    root:
    for ( var index in mimedb ) {
      if ( 'extensions' in mimedb[index] ) {
        for ( var indexExt in mimedb[index].extensions ) {
          if ( mimedb[index].extensions[indexExt] == extInput ) {
            if ( index.split('/')[0] == 'image' ) {
              fileType = 'image';
            } else if ( index.split('/')[0] == 'video' ) {
              fileType = 'video';
            } else {
              fileType = 'other';
            }

            break root;
          }
        }
      }
    }

    if ( extInput == 'pdf' ) {
      fileType = 'image';
    }

    if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
      var url = input.split("/");
      var url_filename = url[url.length - 1];
      var hash = crypto.createHash('sha512');
      hash.update(Math.random().toString());
      hash = hash.digest('hex');
      var temp_input = path.join(os.tmpdir(), hash + url_filename);
      curlArgs = ['--silent', '-L', input, '-o', temp_input];
      child_process.execFileSync("curl", curlArgs);
      input = temp_input;
    }

    fs.lstat(input, function(error, stats) {
      if (error) return callback(error);
      if (!stats.isFile()) {
        return callback(true);
      } else {
        if ( fileType == 'video' ) {
          var ffmpegArgs = ['-y', '-i', input, '-vf', 'thumbnail', '-frames:v', '1', output];
          if (options.width > 0 && options.height > 0) {
            ffmpegArgs.splice(4, 1, 'thumbnail,scale=' + options.width + ':' + options.height + (options.forceAspect?':force_original_aspect_ratio=decrease':''));
          }
          child_process.execFile('ffmpeg', ffmpegArgs, function(error) {
            if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
              fs.unlinkSync(input);
            }

            if (error) return callback(error);
            return callback();
          });
        }

        if ( fileType == 'image' ) {
          var convertArgs = [input + '[0]', output];
          if (options.width > 0 && options.height > 0) {
            convertArgs.splice(0, 0, '-resize', options.width + 'x' + options.height);
          }
          if (options.autorotate) {
            convertArgs.splice(0, 0, '-auto-orient');
          }
          if (options.quality) {
            convertArgs.splice(0, 0, '-quality', options.quality);
          }
          if (options.background) {
            convertArgs.splice(0, 0, '-background', options.background);
            convertArgs.splice(0, 0, '-flatten');
          }
          child_process.execFile('convert', convertArgs, function(error) {
            if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
              fs.unlinkSync(input);
            }
            if (error) return callback(error);
            return callback();
          });
        }

        if ( fileType == 'other' ) {
          var hash = crypto.createHash('sha512');
          hash.update(Math.random().toString());
          hash = hash.digest('hex');

          var tempPDF = path.join(os.tmpdir(), hash + '.pdf');

          var unoconv_pagerange = '1';
          var pagerange_start = 1;
          var pagerange_stop = 1;
          if (options.pagerange) {
            var pagerange = options.pagerange.split("-");
            if (pagerange.length == 2) {
              unoconv_pagerange = options.pagerange;
              pagerange_start = pagerange[0];
              pagerange_stop = pagerange[1];
            }
          }

          if (unoconv_pagerange == '1') {
            child_process.execFile('unoconv', ['-e', 'PageRange='+unoconv_pagerange, '-o', tempPDF, input], function(error) {
              if (error) return callback(error);
              var convertOtherArgs = [tempPDF + '[0]', output];
              if (options.width > 0 && options.height > 0) {
                convertOtherArgs.splice(0, 0, '-resize', options.width + 'x' + options.height);
              }
              if (options.quality) {
                convertOtherArgs.splice(0, 0, '-quality', options.quality);
              }
              child_process.execFile('convert', convertOtherArgs, function(error) {
                if (error) return callback(error);
                fs.unlink(tempPDF, function(error) {
                  if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
                    fs.unlink(input);
                  }
                  if (error) return callback(error);
                  return callback();
                });
              });
            });
          } else {
            child_process.execFile('unoconv', ['-e', 'PageRange='+unoconv_pagerange, '-o', tempPDF, input], function(error) {
              if (error) return callback(error);
              var pages = [];
              for ( var x = 0; x < pagerange_stop; x++ ) { pages.push(x); }
              async.eachSeries(pages, function iteratee(page, async_callback) {
                var convertOtherArgs = [tempPDF + '['+page+']', page+'_'+output];
                if (options.width > 0 && options.height > 0) {
                  convertOtherArgs.splice(0, 0, '-resize', options.width + 'x' + options.height);
                }
                if (options.quality) {
                  convertOtherArgs.splice(0, 0, '-quality', options.quality);
                }
                child_process.execFile('convert', convertOtherArgs, function(error) {
                  if (error) return callback(error);
                  return async_callback();
                });
              }, function done() {
                fs.unlink(tempPDF, function(error) {
                  if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
                    fs.unlink(input);
                  }
                  if (error) return callback(error);
                  return callback();
                });
              });
            });
          }

        }
      }
    });
  },

  generateSync: function(input_original, output, options) {

    options = options || {};

    var input = input_original;

    // Check for supported output format
    var extOutput = path.extname(output).toLowerCase().replace('.','');
    var extInput = path.extname(input).toLowerCase().replace('.','');

    if (
      extOutput != 'gif' &&
      extOutput != 'jpg' &&
      extOutput != 'png'
    ) {
      return false;
    }

    var fileArgs = [input_original];
    var fileExecOutput = child_process.execFileSync('file', fileArgs);
    var is_executable = fileExecOutput.toString().indexOf("executable");
    if (parseInt(is_executable) > 0) {
      return callback(true);
    }

    var fileType = 'other';

    root:
    for ( var index in mimedb ) {
      if ( 'extensions' in mimedb[index] ) {
        for ( var indexExt in mimedb[index].extensions ) {
          if ( mimedb[index].extensions[indexExt] == extInput ) {
            if ( index.split('/')[0] == 'image' ) {
              fileType = 'image';
            } else if ( index.split('/')[0] == 'video' ) {
              fileType = 'video';
            } else {
              fileType = 'other';
            }

            break root;
          }
        }
      }
    }

    if ( extInput == 'pdf' ) {
      fileType = 'image';
    }

    if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
      var url = input.split("/");
      var url_filename = url[url.length - 1];
      var hash = crypto.createHash('sha512');
      hash.update(Math.random().toString());
      hash = hash.digest('hex');
      var temp_input = path.join(os.tmpdir(), hash + url_filename);
      curlArgs = ['--silent', '-L', input, '-o', temp_input];
      child_process.execFileSync("curl", curlArgs);
      input = temp_input;
    }

    try {
        stats = fs.lstatSync(input);

        if (!stats.isFile()) {
          return false;
        }
    } catch (e) {
        return false;
    }

    if ( fileType == 'video' ) {
      try {
        var ffmpegArgs = ['-y', '-i', input, '-vf', 'thumbnail', '-frames:v', '1', output];
        if (options.width > 0 && options.height > 0) {
          ffmpegArgs.splice(4, 1, 'thumbnail,scale=' + options.width + ':' + options.height + (options.forceAspect?':force_original_aspect_ratio=decrease':''));
        }
        child_process.execFileSync('ffmpeg', ffmpegArgs);
        if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
          fs.unlinkSync(input);
        }
        return true;
      } catch (e) {
        return false;
      }
    }

    if ( fileType == 'image' ) {
      try {
        var convertArgs = [input + '[0]', output];
        if (options.width > 0 && options.height > 0) {
          convertArgs.splice(0, 0, '-resize', options.width + 'x' + options.height);
        }
        if (options.quality) {
          convertArgs.splice(0, 0, '-quality', options.quality);
        }
        if (options.background) {
          convertArgs.splice(0, 0, '-background', options.background);
          convertArgs.splice(0, 0, '-flatten');
        }
        child_process.execFileSync('convert', convertArgs);
        if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
          fs.unlinkSync(input);
        }
        return true;
      } catch (e) {
        return false;
      }
    }

    if ( fileType == 'other' ) {
      try {
        var hash = crypto.createHash('sha512');
        hash.update(Math.random().toString());
        hash = hash.digest('hex');

        var tempPDF = path.join(os.tmpdir(), hash + '.pdf');

        var unoconv_pagerange = '1';
        var pagerange_start = 1;
        var pagerange_stop = 1;
        if (options.pagerange) {
          var pagerange = options.pagerange.split("-");
          if (pagerange.length == 2) {
            unoconv_pagerange = options.pagerange;
            pagerange_start = pagerange[0];
            pagerange_stop = pagerange[1];
          }
        }

        child_process.execFileSync('unoconv', ['-e', 'PageRange='+unoconv_pagerange, '-o', tempPDF, input]);

        if (unoconv_pagerange == '1') {
          var convertOtherArgs = [tempPDF + '[0]', output];
          if (options.width > 0 && options.height > 0) {
            convertOtherArgs.splice(0, 0, '-resize', options.width + 'x' + options.height);
          }
          if (options.quality) {
            convertOtherArgs.splice(0, 0, '-quality', options.quality);
          }
          child_process.execFileSync('convert', convertOtherArgs);
        } else {
          for ( var x = 0; x < pagerange_stop; x++ ) {
            var convertOtherArgs = [tempPDF + '['+x+']', x+'_'+output];
            if (options.width > 0 && options.height > 0) {
              convertOtherArgs.splice(0, 0, '-resize', options.width + 'x' + options.height);
            }
            if (options.quality) {
              convertOtherArgs.splice(0, 0, '-quality', options.quality);
            }
            child_process.execFileSync('convert', convertOtherArgs);
          }
        }

        fs.unlinkSync(tempPDF);

        if (input_original.indexOf("http://") == 0 || input_original.indexOf("https://") == 0) {
          fs.unlinkSync(input);
        }
        return true;
      } catch (e) {
        return false;
      }
    }
  }
};