Compression Modes with Memjet Engines

February 6, 2014

Desktop printing systems based on Memjet technology present unusual tradeoffs between reliability and image quality. This is because the internal design of the Memjet system depends on "image compression" to help it to handle high data rates. This is a special issue for the roll-fed versions of these devices, where failure to achieve sufficient compression can result in prints that fail. The typical failure is for the device to simply stop part way through the print, wasting time and media.

The Memjet system provides two types of compression. The first is closely related to "jpeg" compression, and involves the type of image loss associated with that compression. On prints, this appears as "fuzzy edges" and "scattered dots", particularly at the edges of typesetting and barcodes.

The second type of compression is closely related to Tiff "packbits". It does not cause any loss of image quality, but it is only effective for black and white, or for large areas of solid color. On any job that involves photorealistic imagery, it may fail to provide sufficient compression, causing costly failures of the Memjet system during printing.

Because the first type of compression is the only one shown to be universally reliable in our tests, Wasatch SoftRIP only provides that type of "lossy" compression as shipped. Alternatives are available in SoftRIP, but only under a special registration code that is available on request.

Default installations will display Speed Graphics as the only avalable compression mode. This will apply the 'jpeg' style compression, and suggest a conservative setting for the quality of that compression to optimize reliability. Failures are possible, but unlikely.

Additional Modes available under code: MEMJETENABLECOMPRESSION

Text + Barcodes: Image data will be losslessly compressed. This selection should only be used with simple print files, generally only vector text and barcodes. If print files are overly complex or difficult to compress errors may occur at print time. This is likely to be a good choice for "tag and trace" labeling work that does not involve photo-realistic components.

Auto-Optimized: Image data will be analyzed by Memjet's software to determined areas of print data to be compressed lossy and areas of print data that can be losslessly compressed. This compression mode has been prone to failure due to Memjet's logic to determine what areas of the source file can be losslessly compressed. Areas that contain colors that differ greatly, for example CMYK 0, 0, 0, 0 next to elements with a color of CMYK 255, 255, 255, 255 or 0, 0, 0, 255 are flagged for lossless compression. This logic can flag image data that is difficult to compress losslessly causing data starvation.

VDP Stencil: This compression mode is used in conjunction with SoftRIP's Variable Data Printing feature. Fields created in VDP will be losslessly compressed while the remaining background image is compressed using the JPG Quality Mode settings. The background image data will only be sent once for each print spooler launch. The remaining records will only send the variable data, resulting in less data being sent. Similar to the 'Text + Barcodes' mode this option is prone to failures with jobs that cannot be adequately compressed.