To set a color to be masked, simply specify its alpha channel value as negative. Color masking should be used for the old shading algorithm ('set gxout shade1') or when drawing shapefiles with the polygons set to be filled. In version 2.1+, shade2 is the default algorithm used for 'set gxout shaded'. It is not necessary to use masked colors for "set gxout shade2" because the new shaded contouring algorithm is very well behaved. It is a good idea to avoid using masked colors unless absolutely necessary. There may also be a performance penalty for using masked colors. The masked region is an image operation, so the boundaries may appear jagged - pixelated - if the plot is rendered at sufficiently low resolution. There are some drawbacks to using masked colors. When this action is terminated, at the conclusion of a 'draw' or 'display' command or when another color number is being used, then the "masked" color is drawn to the main plot using a masked paint operation, where the color is painted to the plot everywhere where the mask image was 1. The mask image can be thought of as simply zeros and ones - 0 indicating that the color has not been drawn there, 1 that it has. While that color number is being plotted, the plotting is done to the mask image instead. When the masked color number is encountered, a mask is set up, the same size of the screen image. How this operates "under the hood" is somewhat like double buffering. To avoid this, you can plot a semi-transparent color value using a color mask. This is due to the alpha channel value being applied twice to the same set of pixels. When filling such an area on the plot using a semi-transparent color, spurious lines may appear at the polygon boundaries or in areas where the polygons overlap. The filled areas usually consist of a large number of polygons that appear as one solid region. Starting with GrADS version 2.1, there is an addional optional argument that may be used to set a transparency level for a user-defined color.Ī filled region on a plot is achieved by shaded contouring, filling land/ocean areas using basemap.gs, or drawing a shapefile with filled polygons. White will be the color in the center of the new anomaly Of blue and red that range in intensity from fully saturated to very Plotting anomalies, you can define new colors that will be shades It is possible for the user to define new colorsįor example, to create a palette of colors for Shades command to get information about the contour levelsįor some graphics, the 16 GrADS default colors may not be
The scripts "cbar.gs" and "cbarn.gs" willĭraw a color key alongside a plot of filled contours or shaded grid Of default contour intervals for filled contours and shaded grid The same principle is behind the selection When drawing contour plots, the default behaviour of GrADS is to colorĬode the contours and select an appropriate contour interval so thatĮach contour is a different color and the colors span the range of theĭefault rainbow sequence. GrADS creates a default rainbow palette using the following sequence of 13 built-in colors: Of the default colors numbered 0 to 15 are given below:ġ foreground 255 255 255 (white by default)ĭisclaimer: The color samples may not be displayed properly. Every color in GrADS has a unique color number that is usedĪs an index to identify it in GrADS commands. GrADS is built with 16 default colors that are used in a variety ofĪpplications.
Controlling Colors in GrADS Controlling Colors in GrADS
0 kommentar(er)
