Saturday, April 7, 2012


I would hazard the guess that nine out of any ten rock art enthusiasts have tried to enhance faint pictographs by software manipulation of the image in their computer. I will also hazard the guess that for at least 8 of that 9 the results were less than satisfying. There is now new software that seems to provide amazing results.

An article by Renata d’Aliesio in the Toronto Globe and Mail, Thursday, March 15, 2012, describes this apparently miraculous new tool which its developer Jon Harman has named DStretch. D’Aliesio described the circumstances leading up to its development like this: "Rock art had long fascinated Jon Harman. The American mathematician sought out pictographs on vacations, snapping pictures of stones and caves even when all that remained were indecipherable red blotches. Photo-editing programs improved the images, but not by much. A friend pointed Mr. Harman to an image-enhancement technique known as decorrelation stretch. Developed by NASA’s Jet Propulsion Laboratory, it has been used to enhance photos of Mars. Perhaps the technique would work for faded pictographs. Mr. Harman took up the challenge and, with a few modifications, DStretch was created in late 2005. He provides the plug-in at no cost through his website ( . It’s designed to work with the ImageJ program, on PCs and Macs.”
A couple of photographs from the article in the Globe and Mail can illustrate the results.

Sinclair Creek in Kootenay National Park,
B.C. Photograph Toronto Globe and Mail

The person on the left is dancing within a rayed arc, "depicting a shamanistic activity. This was a common image among central Columbia Plateau aboriginal groups, but less so in eastern British Columbia, where this pictograph is located. The triangular-shaped figure on the right is of a different rock art tradition and may have been painted at a different time. In the figure’s hand is a circle or drum, indicating a ceremonial activity."

Washout Creek along the shore of Kootenay Lake,
B.C. Photograph Toronto Globe and Mail.
Multiple figures were painted at the Washout Creek site, "often overlapping, indicating these pictographs were created over a long period of time – likely hundreds or even thousands of years. Drawings of a human figure with a drum and fir boughs suggest ceremonial activities took place here. Fir boughs were used in cleansing ceremonies of young females who had completed a vision quest. Vision quests marked the transition from childhood to adulthood for many Columbia Plateau groups. Also shown is a person hunting for sturgeon with a long spear, illustrating this was a good fishing spot."

Parks Canada has been photographically recording rock art sites to preserve the images. A spokesman for Parks Canada, a Mr. Himour said that for them DStretch proved to be a real game changer. They first used the software in the summer of 2010, applying it to photos taken at Sinclair Creek in British Columbia’s Kootenay National Park. Unlike the cross-polarization technique, pictures could be taken during the day. No special filter or flashes were required. They have taken about 2,500 photos at 30 rock art sites in Kootenay and Banff National Parks and in the foothills of Alberta as part of its Pictograph Project. Many of the known pictograph sites have faded so badly that they cannot see images that had already been recorded at the sites. With DStretch, however, these images can be retrieved and seem to jump out at the viewer. While the article in the Globe and Mail only mentions pictographs I also wonder if this software might be sensitive enough to bring out those repatinated petroglyphs that can be so hard to photograph under many lighting conditions. Perhaps those of us with a technical bent can make use of this software in our own photo collections to preserve the precious images that are inexorably fading.

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