Microsoft Office Compression

Microsoft Office files contain an abundance of content that can be optimized; from oversized images and old fast save information to hidden data in embedded objects. NXPowerLite can selectively optimize each of these elements within the files to create leaner, smaller documents, spreadsheets and presentations.


Image resizing

Images are often inserted into Microsoft® Office documents at much larger sizes than necessary. For example, a photograph taken by a digital camera might contain five million or more pixels, but most of this detail will not be visible unless ‘zoom’ controls are used. NXPowerLite can scale down such images by a configurable amount. For example, if NXPowerLite is configured to optimize PowerPoint® files for viewing at 1600x1200 pixels (the default setting), any images which fill an entire slide and are larger than 1600x1200 pixels will be scaled down to 1600x1200 pixels (sufficient for nearly all viewing and printing purposes).

Note: Resizing can be enabled or disabled and specific resolutions configured in the “Image Optimization” tab of the “Settings” dialog


JPEG conversion & compression

NXPowerLite can convert certain types of image to JPEG format, which offers high compression levels but can affect image quality. NXPowerLite can also apply additional compression to images that are already in the JPEG format. The default setting (7) will result in a barely noticeable loss of quality, even at 100% zoom.

Note: JPEG compression/quality level can be configured in the “Image Optimization” tab of the “Settings” dialog


Metafile conversion

Microsoft® Office documents often contain images in WMF (‘Windows Metafile’) and EMF (‘Enhanced Metafile’) formats, which are suitable for vector graphics but are highly inefficient for representing bitmapped images (e.g. screenshots or photographs). Wherever possible, NXPowerLite will convert such images to PNG or JPEG format.


Removes "fast save" information

PowerPoint® 2003 and earlier have the option to enable 'Fast saves'. This has the effect that in some cases, deleted or edited objects will not be removed from the PowerPoint® file when changes are saved. NXPowerLite removes this 'fast save' information, preserving only the most recent edit. Previous edits are not available through PowerPoint’s® user interface anyway, but forensic tools may be able to extract some historical information from a ‘fast saved’ file.


Removes unnecessary metadata

Some image file formats (e.g. PNG or JPEG) allow additional metadata to be embedded in the image file. For example, JPEG files created by a digital camera may contain EXIF information which indicates the type of camera used, where the photograph was shot and date that it was taken. NXPowerLite removes any data which is not required to display the image.


Removes cropped areas of inserted images

After inserting an image into a Microsoft® Office document, it is possible to request that the image be 'cropped'. This option is available by right-clicking on an image and selecting 'Size and Position...' in Office 2007 or later, or 'Format Picture...' in earlier versions of Office. Cropping causes only part of the image to be displayed, although the entire image is preserved when the file is saved, so it is possible to undo or change the amount of cropping later. If NXPowerLite is configured to discard cropped image data, the non-visible parts of images will be removed, so will not be recoverable after optimization.

Note: Removing cropped areas of images can be enabled or disabled or set to occur in files that haven’t been modified within a specified timeframe. This is configured in the “Hidden Content” tab of the “Settings” dialog.


Flattens embedded objects

Embedded objects (e.g. an Excel® chart embedded in a PowerPoint® presentation) are saved in Microsoft® Office documents with two representations - a 'picture' representation and a 'native' representation. If NXPowerLite is configured to flatten embedded objects, it will remove the 'native' representation, which can significantly reduce the size of files, but flattened objects can no longer be edited in the application in which they were created.

Note: Flattening embedded objects can be enabled or disabled or set to occur in files that haven’t been modified within a specified timeframe. This is configured in the “Hidden Content” tab of the “Settings” dialog.