Show Elements by Patina
Objective
The Show Elements by Patina function sorts the cropped rock art elements for the selected survey by the differences in color values between the pecked or repecked area and the natural patina color value. The color values are derived from nine pixels inside a 3 by 3 pixel area under selected pecked, repecked or natural patina area on the images. Each pixel has a red, green and blue value between 0 and 255. The color value is the summation of the average value of each color. The smaller the color value, the darker the color (e.g. black equals 0, white equals 255).
This technique is similar to the use of the Munsell System of Color Notation used in traditional rock art recording in that it is intended to be used to estimate the relative age of an element. In most circumstances, the results are very inaccurate. There are many difficulties that lead to inaccurate results, including:
- differences in exposure when multiple photos are used.
- differences in the natural patina on multiple panels or even the same panel.
- the texture of the rock creates tiny shadows and hot spots.
- bumps and curves in the panel will cause the color to appear different when it is the same.
- shadows, making the rock look darker.
- hot spots, making the rock look lighter.
Processing
The first page will display a list of surveys on the database.
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Hyperlinks include: Area (see ShowMaps).
To continue, select a survey by clicking on the Ref Nbr of a survey.
The second page displays a table of all the panels and number of rock art elements in each panel. You may select any number of panels by clicking on a panel's check box or none to select all panels. The best results will be obtained by choosing only one panel and using only one image because differences in panel patina and image exposure will distort the results.
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To continue, click the Submit button.
The third page displays the cropped rock art elements sorted by the default or selected sorting sequence. Underneath each element is a table showing the average red, green, blue values and their totals for the pecked (P) or repecked (R) areas, the natural (N) patina and the differences in averages.
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Hyperlinks include: Rock Art Class, Element ID, RGB, Cluster, Panel, Element (see ElementCaptions), Prior Page, Next Page (see PageNumbers).
Identifying pecked, repecked and natural patina points when the element is recorded is optional. Elements without patina points will not be shown. Elements with both pecked and repecked areas identified will be shown twice, once with the pecked values and once with the repecked values.
The bottom of the page shows the three sets of radio buttons used to control the sort sequence. You may change the sort control and click the Change Sort button. The page will be redisplayed with the changed sort sequence.
Sort options include:
- Sort by differences in value between pecked area and natural patina
- Sort by raw value of pecked area color
- Sort by total value of all colors
- Sort by red color
- Sort by green color
- Sort by blue color
- Show oldest elements first - this assumes the older the element, the smaller the difference between the pecked area and natural patina.
- Show youngest elements first - this assumes the younger the element, the greater the difference between the pecked area and natural patina.
Buttons
Submit: accepts the request and takes the application to the next page.
Reset: resets to the page to the last values displayed by your browser.
Change Sort: accepts the sort control request and redisplays the page.
Change Panel: take you to the second page displaying a table of the panels of the chosen survey.
Change Survey: takes you to the first page displaying a list of surveys and the sort selections.
Next Page: take you to the next page.
Prior Page: takes you to the prior page.
Menu: takes you to the Main Menu.