DStretch Tutorial Examples
show different techniques for image enhancement using DStretch.
first two examples are from Cueva San Borjita, a Great Mural site near
Mulege, Baja California Sur. The third is from Cueva Raton, a
Great Mural site north of San Ignacio, Baja California Sur.
The fourth is from the Carrizo Plain, California. A Chumash site
on the old Saucito Ranch, SLO-336.
The images in the examples are highly compressed jpeg's. They are
not suitable for DStretch enhancement. For those who might want
to try their own enhancements on these images I am including the
originals in low resolution, but only slightly compressed form. Image for Example 1 (San Borjita
for Example 2 (San
for Example 3 (Cueva Raton)
for Example 4 (Saucito Ranch) Image for Example 5 (Agua del
Ganado). These images are also available when using the
applet and can be opened using
the open samples menu.
Additional help for using DStretch: DStretch Help
the differences between colorspace choices and between mapped back
and not mapped back.
Example 2 shows the
use of enhancement in clarifying pictograph
composition by improving contrast. I enhanced the image using the
RGB colorspace, not mapped back. Then I hue shifted the image by
140 degrees to get better contrast.
Example 3 demonstrates
the use of the custom RGB matrix. The
first enhancement is LAB, mapped back. The colors are enhanced
and blacks and the wall surface features are still visible. The
second enhancement uses the CRGB button. This
surface features and makes the red colors more prominent. It
helps to clarify the original composition. The price to pay for
this is the supression of black or white pictographs. Note that
black "rat", actually a puma, nearly disappears in the custom RGB image.
demonstrates the use of area selection. The original image
includes a green bush on the left. This affects the
enhancement. By choosing an area selection avoiding the bush one
gets a better enhancement. ImageJ has many different area
selection tools. In this case I used a rectangle, but ellipses,
polygons, and freehand drawing are also available. By making very
small area selections you can create very different enhancements,
sometimes getting interesting effects.
demonstrates the use of hue masking. Agua del Ganado is a very
poorly preserved site. The rock is flaking off the walls, taking
the paint with it. I use a CRGB enhancement to bring out a bird
pictograph then I hue mask the result to isolate the hues in the
bird. This is not entirely successful since the same hues exist
outside the bird, but in a random pattern. I
reduce the noise points outside of the bird by using cleaning techniques. Finally I add the result back
into the original image.