lib/url/imageurl.js
function(options) {
        var params = [],
            opts = options || {},
            transform = 'contrast';

        if (opts.sharpen) {
            params.push('sharpen=' + opts.sharpen);
        }

        if (params.length) {
            transform += ':' + params.join(',');
        }

        return this.append(transform);
    }
function(options) {
        var params = [],
            opts = options || {},
            transform = 'contrast';

        if (opts.sharpen) {
            params.push('sharpen=' + opts.sharpen);
        }

        if (params.length) {
            transform += ':' + params.join(',');
        }

        return this.append(transform);
    }
function ( options ) { var params = [ ] , opts = options || { } , transform = 'contrast' ; if ( opts . sharpen ) { params . push ( 'sharpen=' + opts . sharpen ) ; } if ( params . length ) { transform += ':' + params . join ( ',' ) ; } return this . append ( transform ) ; }
Adjust contrast in the image

@param  {Object} [options={}]
@param  {Number} [options.sharpen] Change in contrast given as number of steps up (positive
number) or down (negative number)
@return {Imbo.ImageUrl}
Adjust contrast in the image