How do I ...? > Appearance > 256 colour mode vs. high colour mode

GRAPH-XT supports two colour modes: 256 colour mode (the default) and high colour mode.

If you specify 0 for the Target variable (or omit this variable completely) for the è DPlot_show function a colour depth of 256 colours is used. In this case the bitmap file will be loaded into the HTBasic bitmap memory using GLOAD and can be manipulated with the normal plot commands like PLOT, LABEL, RECTANGLE etc.

If you set the parameter Target to >0 a colour depth of millions of colours is assumed (also called "high colour mode") and the diagram will be loaded into a Basic Plus Bitmap widget. Using this method you can display diagrams with millions of colours but with the down side that these widgets can’t be easily DUMPed to a printer (since the Basic Plus Bitmap widget DUMP routine does not support more than 256 colours) which will result in false colours when doing a DUMP GRAPHICS. In high colour mode it is also not possible to use HTBasic graphics commands (which shouldn't be necessary in most cases, though), and Kanji is therefore not supported in this mode.

What colour mode should I use?

If you need to mix the HTBasic graphics commands with the diagram created by GRAPH-XT you must use the 256 colour mode. Also, if you need the DUMP GRAPHICS command in order to print the diagrams, the 256 colour mode must be used. Kanji is also only supported in 256 colour mode.

If you want to display shaded 3D graphics the high colour mode is recommended. You can also print these diagrams, but if you use HTBasic for printing the colours will be reduced to 256 colours in the printout which leads to false colours. For high quality prints of 3D graphics you should better use the DPlot [FilePrint()] macro command.

If you are using the high colour screen mode a Basic Plus bitmap widget will be used for displaying the graphics. In this case you can't mix the graphics with HTBasic graphics commands anymore (also: no Kanji support in this mode).

Additionally, in high colour mode the following info is shown while a new graphic is created:

Shaded 3D example plot in 256 colour mode:

clip0062

The same 3D example plot in high colour mode:

clip0063

As you can see the diagram in high colour mode looks much smoother for those shaded 3D diagrams because no colour interpolation is necessary. For normal diagrams without colour shading, however, the high colour mode is not needed.

SEPARATE ALPHA FROM GRAPHICS

If you use SEPARATE ALPHA FROM GRAPHICS mode please note that the colour mapping is most likely different in 256 colour mode compared to MERGE ALPHA WITH GRAPHICS mode. This can be solved by creating a customized colour mapping in SEPARATE ALPHA FROM GRAPHICS mode.