If this option is checked, the log (base 10) of the values are mapped.
Gamma adjustment alters the distribution of color in the key. It is frequently used to increase contrast at low intensities in order, for example, to compensate for the non-linearity of display systems. A gamma adjustment of 1 results in no correction. 0.7 to 1 is recommended.
Center color on this value
High end color
Low end color
Color for undefined values
The color of an element in the map is scaled (linearly for gamma = 1 (no correction)) between the center color to the high or low end color (for above or below the center value, respectively). The center color should be between the highest and lowest values in the map (inclusive). It can be specified as an exact numeric value or by "min", "max", "mean", or "mid", representing the minimum or maximum values in the map, the mean value found in the map, or (max+min)/2.
An additional color is used to represent undefined values in the map.
Use separate scales above and below the center value
The method of scaling the colors depends on this option. If it is checked, the minimum value in the map is represented by the low end color, and likewise the maximum value in the map is represented by the high end color. The colors of each value in the map are scaled between these values and the center.
This is not always desirable. For instance, it is often more meaningful to show the magnitude of the distance from the center with the same intensity, regardless of whether it is above or below the center. However, in other cases (especially when the ranges above and below the center differ greatly), it is desirable to use separate scales for the high and low ends.
Width of map element
This specifies the width of the elements in the map, in pixels.
Height of map element
This specifies the height of the elements in the map, in pixels.
An image is generated depicting the map, with labels from the rows and columns taken from the source data, if available. If labels are not available, the row and column numbers are used. A key is also generated within the image showing the colors for different values in the map.