How Lucis Works

Lucis processing has two steps. The first step is to contrast stretch the image to use the full range of contrasts. So if you process an image with Lucis and do not alter the sliders the image will be contrast stretched. Then contrast differences that are greater than the Smooth Detail slider but less than the Enhance Detail slider are enhanced, and contrast differences outside this range (meaning less than or equal to the Smooth Detail slider and greater than or equal to the Enhance detail slider) are diminished.

Lucis shifts the relative emphasis of contrast variances so the user can more clearly see contrast variances of interest. Lucis does not throw away data.

For this first example 16-bit tiff images were used. The images posted are the results converted to 8-bit jpeg images.

Image 1 is the original 16-bit x-ray image. It only used 25,227 levels of contrast. Lucis was used to contrast stretch the image to use the full range of contrasts (in this case 62,569 intensity levels). This is shown in Image 2.

The test image (Image 3) was created by making a image that was transparent except for a black stripe and using layers in Photoshop to merge the striped image at 90% opacity with Image 2. So now the intensity differences within the black stripe are diminished by 90%.

In Image 3 the Enhance Detail slider was set to 3363. (Image smoothing was not required so the Smooth Detail slider was not used.) This means that contrast differences less than 3363 were enlarged and contrast differences greater or equal to 3363 were diminished. Lucis accurately enhances the smallest differences in contrast throughout the image using just one slider.


Origin X-Ray Image

Image 1. Original X-Ray Image

Contrast Stretched Image

Image 2. Contrast-stretched image.

Lucis Pro Image

Image 3. Test image with a black stripe at 90% opacity.

Lucis Pro Image

Image 4. The Lucis-processed image.

This next image is a test image developed by Professor Brian Matsumoto. (For more information, please read the white paper.)

Professor Matsumoto created an 8-bit grayscale test pattern with differing lines and shaded areas. This 8-bit test pattern uses the full range of intensity levels, namely 257. He replicated this test pattern in the top right and bottom left corners of this test image. Then he mapped this test pattern to the smallest 16 intensity levels and placed this modified test pattern in the bottom right part of the test image. Finally Professor Matsumoto mapped the test pattern to the brightest 16 intensity levels and placed this modified test pattern in the top left quadrant of the test image. So the white and black portions of this image have pixels whose contrasts vary by 16 intensity levels or less. We cannot see very much detail even though a great deal of detail is present. 

Lucis reveals the image information simply by moving the Enhance Detail slider to 9 (Image 3).

Lucis Pro Image

Image 1. Original test image.

Lucis Pro Image

Image 2. Histogram of the original test image.

Lucis Pro Image

Image 3. Lucis image.

Lucis Pro Image

Image 4. Histogram of the Lucis image.