Paul G. Roetling

Aesthetic measures for automated document layout

A measure of aesthetics that has been used in automated layout is described. The approach combines heuristic measures of attributes that degrade the aesthetic quality. The combination is nonlinear so that one bad aesthetic feature can harm the overall score. Example heuristic measures are described for the features of alignment regularity separation balance white-space fraction white-space free flow proportion uniformity and page security.

Fourier spectrum of halftone images

An analytic expression has been developed that can be used for computing the Fourier spectrum of any halftone image as a function of the original continuous-tone image and the halftone process. This result takes into account the nonlinear effects of the threshold step in the halftone process. Although the result is general and can be applied to any original image, in some cases of periodic images the Fourier components of the halftone image are particularly easy to compute. We show important differences between spectra of halftone images and scanned or sampled images. In halftone images, significant image detail is maintained at spatial frequencies greater than half of the screen frequency and aliasing or moire patterns depend upon object contrast and upon the halftone function differently from similar patterns which occur in scanned or sampled imagery.

Halftone method with edge enhancement and Moiré suppression

A method has been found for separating control of high and low spatial frequencies in a continuous-tone image during conversion to a halftone (binary) form for printing. This method allows edge enhancement, while simultaneously limiting creation of spurious Moire patterns due to image frequencies near the halftone screen frequency. Macroscopic grey scale control is achieved by determination of average grey level by low-pass filtering of the image. This information is used to set halftone dot size. Microscopic or detail contrast is controlled as in the ordinary halftone process, that is, by screen shape and screen modulation, which therefore affects partial dot structure. In the absence of detail, the results of this process match ordinary halftones. In detailed areas, however, the low-frequency control limits generation of spurious low-frequency Moire patterns, while free choice of screen modulation allows enhancement of edges up to the common limit where image noise becomes dominant.

Visual Performance And Image Coding

Sample spacing and quantization levels are usually chosen for digitizing images such that the eye should not see degradations due to either process. Sample spacing is chosen based on the resolution (or high frequency) limit of the eye and quantization is based on perception of low contrast differences at lower frequencies. This process results in about 8 bit/pixel, 20 pixel/mm digitization, but, being based on two different visual limits, the total number of bits is an overestimate of the information perceived by the eye. The visual MTF can be interpreted in terms of perceptible levels as a function of spatial frequency. We show by this interpretation that the total information perceived by the eye is much less than 8 bits times the number of pixels. We consider the classic halftone as an image coding process, yielding 1 bit/ pixel. This approach indicates that halftones approximate the proper distribution of levels as a function of spatial frequency; therefore we have a possible explanation of why halftone images retain most of the visual quality of the original.

Editorial: The Changing of the Guard

This PDF file contains the editorial “Editorial: The Changing of the Guard” for JEI Vol. 3 Issue 04

Editorial: Another Year Has Passed

This PDF file contains the editorial “Editorial: Another Year Has Passed” for JEI Vol. 3 Issue 01

Editorial: Is This Your Journal?

This PDF file contains the editorial “Editorial: Is This Your Journal?” for JEI Vol. 2 Issue 04

Editorial: A Year Has Passed

This PDF file contains the editorial “Editorial: A Year Has Passed” for JEI Vol. 2 Issue 01

Editorial: JEI Is Evolving

AlthoughJEt may appear much the same from issue to issue, we are very much in a state of continuing evolution. Each year, at the Electronic Imaging meeting in San Jose, we meet with our Editorial Advisory Board and the Coordinating Committee to discuss the state of JEI and where it should be going. Their advice, plus what we hearfrom readers and referees, provides guidance for our future. One conceptthat has been suggested by various sources since our inception has been to include special sections on topics of interest. As editor, I chose not to include such sections in our first year; instead, I accepted manuscripts across a broad range of topics in electronic imaging to prevent biasing potential authors by concentrating on any given topic. We have, indeed, covered many topics and have a broad range of contributors. We have, therefore, decided to try something new, and I am pleased to announce that our first special section is now in progress. Eric Hanson of Hewlett Packard is our guest editor for a section on nonimpact printing. A number of papers have been submitted and are now in the peer review process. The special section should be ready to appear in an issue soon. Another concept that has been suggested is a section describing electronic imaging research at a given university. Unlike some similar ideas you may have seen elsewhere, we plan to present such a topic at the same technical level as other parts of the journal. The section would consist of a brief introduction about the organization, followed by a few technical papers. The papers would be reviewed like any others in the journal, but by grouping them, the range of work being performed in the organization will be shown. We are talking to several people, but do not yet have a firm commitment for a section. If you are interested, contact me at the address on the masthead. In a previous editorial, we suggested that JEI might start a correspondence section containing discussion about previously published papers. We would publish submitted comments, along with the authors response. Is anyone interested? Not all the changes in JEI are visible to our readers. We now have all of our records on a database system on UNIX. The system reminds us aboutthings like acknowledgment letters, so if you submit a manuscript and it is not acknowledged, it probably means we did not receive it. As our base of both manuscripts and referees grew, we needed to make our system somewhat more automatic. Finally, we have not forgotten our promise to update the methods we offer our authors for submitting manuscripts. (As we have said previously, we will accept floppy disks with ASCII text.) To get our project moving, we have recruited Gary Starkweather, an Apple Fellow, to assist us in examining our current procedures and to help in suggesting ways that we can begin to accept input in digital form. If you are a prospective author, we would like to hear from you regarding what your digital system is like, especially what printing capabilities you have and what output formats you can generate for text, graphs, and illustrations.

Editorial: The Unsung Heroes

This PDF file contains the editorial “Editorial: The Unsung Heroes” for JEI Vol. 1 Issue 03