signalSuccess = function() {
                    log("Success generating scaled version for " + sourceFile.name);
                    var blob = qq.dataUriToBlob(scaledImageDataUri);
                    scalingEffort.success(blob);
                }
Controls generation of scaled images based on a reference image encapsulated in a `File` or `Blob`.
Scaled images are generated and converted to blobs on-demand.
Multiple scaled images per reference image with varying sizes and other properties are supported.

@param spec Information about the scaled images to generate.
@param log Logger instance
@constructor