BBTools

bbimagein

This function is not yet fully documented. This is a transcript of the text-formatted help.

bbimagein  Display an image in gray-scale.
   H=bbimagein(C) displays the matrix C as a gray-scale image. C must
   be an H-by-W matrix of doubles. It is somewhat similar to H=imagesc(C)
   followed by colormap(gray), except the image is corrected for the
   non-linear response of the display.

   A standard monitor is non-linear with respect to intensity images, and
   only roughly approximates brightness. Brightness is defined in terms
   of human perception, and is a non-linear function of the intensity.

   Most monitors conforms to the sRGB-specification, which approximates a
   gamma-curve of gamma=2.2. This function creates a color-map which
   compensates for this. The following options are available:
     'intensity' - Show an intensity image (default)
                   AKA: 'i', 'linear', 'lum', 'luminance'
     'light'     - Show a lightness image
                   AKA: 'l', 'bright', 'brightness', 'lightness'
     'noadjust'  - Respect color limits without adjustment

   Intensity images:
     An intensity image is an image that represents intensity (watts per
     unit), luminance (weighted radiant power), or other physical
     quantity that relates linearly to these.

     In a nutshell: a pixel of intensity 2*v should be twice as intense,
     not bright, as one of intensity v. 

     If a linear image is viewed without correction, it will appear dark
     and dull. It is tempting to work in the non-linear color-space of
     the display (many image editing programs do), but this often leads
     to incorrect results.

     For example, a convolution is entirely incorrect when it is
     performed in a non-linear space. Almost any serious computation
     should be done in a linear color-space.

     To work with images from a digicam, you should ensure that the image
     is in a linear color-space. Most digicams converts an image to sRGB
     internally, to match the monitors. A reasonable approximation to
     invert this is IMG=IMG.^2.2.

   Lightness images:
     Lightness is the perceptual response to luminance. In such an image,
     a pixel with value 2*v should appear twice as bright as one of
     brightness v. For many purposes, this is adequately approximated by
     the monitor.

     Nevertheless, the monitor gamma and lightness are not identical,
     with the most noticable difference being near black.
     bbimagein corrects for this difference.

   Like imagesc, you may specify the intensity range. The lower limit is
   black, while the upper limit is white.

   Normally, the specified limits determines the range display in gray.
   This range is expanded to show out-of-range values as described below.
   If the color specified limits is a vector with 4 values, then the
   first and last values represents the complete range displayed.

   Clipping. Both intensity- and brightness-images are, by definition,
   non-negative. However, negative results often occur in computations.
   bbimagein shows negative pixels in green, with a luminance that
   reflects the absolute value. Pixels exceeding the upper limit are
   shown in yellow.

   The colors were chosen because they have a larger dynamic range within
   the gamut than e.g. red and blue.

   Example 1: show a linear image.
     IMG=double(imread('bird_bw.png'));
     bbimagein(IMG); axis image OFF; colorbar;

   Example 2: show clipping of negative values for intensity images.
     bbimagein(-25:125,[0,100]); colorbar;

   See also , , bbphantom.

bbhankelbbindex