Localized Contrast Enhancement — Detailed Results

Data Used

The cuneiform tablet is item "Spalding 1, Ur III", on loan from Gordon Young. The input data was obtained by simply scanning the tablet on a flatbed document scanner at 600 dpi. Thumbnails of the original unenhanced scans are:

**Cuneiform tablet, Spalding 1, Ur III, faces**
Obverse face	Reverse face
1st row	1st row (over top edge)

2nd row	2nd row

3rd row	3nd row

4th row	4th and 5th row

5th row

The 600 dpi resolution results in the following dimensions of the regions considered when remapping each pixel:

Dimensions of Localized Histogram Equalization
Radius			Area
pixels	inches	mm	pixels²	inches²	mm²
100	0.1667	4.2333	31415	0.08727	56.3008
50	0.08333	2.1167	7853	0.02182	14.0752
25	0.04167	1.0583	1963	0.005454	3.5188
12	0.02	0.508	452	0.001257	0.8107

Format of data presentation

Each initial image will be analyzed in turn. The images will show:

Initial image
Global histogram equalization
Localized histogram equalization, radius of 100 pixels
Localized histogram equalization, radius of 50 pixels
Localized histogram equalization, radius of 25 pixels
Localized histogram equalization, radius of 12 pixels

The images shown here are actually downsampled 50%x50% from the originals to reduce the size of this page from 26 MB to 8.3 MB! As an added benefit, it does allow you to compare results from three or four radii (assuming you have a 1024x768 display).

Cuneiform tablet, Spalding 1, Ur III, obverse face, 1st row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, obverse face, 2nd row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, obverse face, 3rd row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, obverse face, 4th row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, obverse face, 5th row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, reverse face, 1st row (over top)

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, reverse face, 2nd row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, reverse face, 3rd row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, reverse face, 4th and 5th row

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, obverse face, rotated 30 degrees toward edge

Note that this image has been rotated 90 degrees for viewing

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, reverse face, rotated 45 degrees toward edge

Note that this image has been rotated 90 degrees for viewing

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Cuneiform tablet, Spalding 1, Ur III, edge

Note that this image has been rotated 90 degrees for viewing

Original image

Global histogram equalization

Localized histogram equalization, radius = 100

Localized histogram equalization, radius = 50

Localized histogram equalization, radius = 25

Localized histogram equalization, radius = 12

Back to the main histogram equalization page.

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© Bob Cromwell Oct 2008. Created with `/bin/vi` and ImageMagick, hosted on OpenBSD with Apache. Root password available here