| .PALETTE Statement Details. |
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 QuickSCREEN Details Example Contents Index |
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| PALETTE Statement Details |
| |
| Syntax |
| PALETTE [attribute,color] |
| PALETTE USING array-name [(array-index)] |
| |
| Argument Description |
| attribute The palette attribute to be changed. |
| color The display color number to be assigned to the |
| attribute. The color must be a long integer expression |
| for the IBM Video Graphics Array adapter (VGA) and IBM |
| Multicolor Graphics Array adapter (MCGA) in screen |
| modes 11 to 13. Integer or long-integer expressions |
| may be used with the IBM Enhanced Graphics Adapter |
| (EGA). |
| array-name An array containing the color numbers to be assigned |
| to the attributes available in the current screen |
| mode. The VGA and MCGA adapters require a long integer |
| array in screen modes 11 to 13. With the EGA this can |
| be either an integer or long-integer array. |
| array-index The index of the first array element to use in setting |
| the palette. |
| |
| The PALETTE statement works only on systems equipped with the EGA, |
| VGA, or MCGA adapters. |
| |
| The statement provides a way of mapping display colors (the actual |
| binary values used by the adapter) to color attributes (a smaller |
| set of values). All BASIC graphics statements such as CIRCLE, COLOR, |
| DRAW, or LINE use color attributes rather than display-color values. |
| |
| When a program enters a screen mode, the attributes are set to a series |
| of default color values. (See the SCREEN statement for a list of the |
| default colors.) In the EGA, VGA, and MCGA adapters these default |
| values have been selected so the display shows the same colors, even |
| though the EGA uses different color values. |
| |
| With the palette statement you can assign different colors to the |
| attributes, giving you greater control over the colors on the display. |
| A PALETTE statement with no arguments sets the palette back to the |
| default color values. |
| |
| When you execute a PALETTE statement with arguments, the adapter |
| subsequently uses the display color (indicated by color) whenever |
| the value attribute appears in a statement like DRAW or LINE that |
| specifies a color. Changing the display color assigned to an attribute |
| changes the color on the screen immediately. |
| |
| For example, assume that the current palette contains colors 0, 1, |
| 2, and 3 in the four attributes numbered 0, 1, 2, and 3. The DRAW |
| statement |
| |
| DRAW "C3L100" |
| |
| selects attribute 3, and draws a line of 100 pixels using the display |
| color associated with attribute 3, in this case also 3. If the |
| statement |
| |
| PALETTE 3,2 |
| |
| is executed, then the color associated with attribute 3 is changed |
| to color 2. All text or graphics currently on the screen displayed |
| using attribute 3 are instantaneously changed to color 2. Text or |
| graphics subsequently displayed with attribute 3 are also displayed |
| in color 2. The new palette of colors contains 0, 1, 2, and 2. |
| |
| With the USING option, all entries in the palette can be modified |
| in one PALETTE statement. The array-name argument is |
| the name of an integer or long-integer array and the array-index |
| specifies the index of the first array element in the array-name |
| to use in setting the palette. Each attribute in the palette |
| is assigned a corresponding color from this array. The array must |
| be dimensioned large enough to set all the palette entries after |
| array-index. For example, if you are assigning colors to all 16 |
| attributes, and the index of the first array element that is given |
| in your PALETTE USING statement is 5, then the array must be |
| dimensioned to hold at least 20 elements (since the number of |
| elements from 5-20, inclusive, is 16): |
| |
| DIM PAL%(20) |
| . |
| . |
| . |
| PALETTE USING PAL%(5) |
| |
| A color argument of -1 in the array leaves the attribute |
| unchanged. All other negative numbers are invalid values for color. |
| |
| You can use the COLOR statement to set the default foreground |
| color and the background display color. The foreground color argument |
| specifies the way text characters appear on the display screen. Under |
| a common initial palette setting, points colored with the attribute |
| 0 appear black on the display screen. Using the PALETTE statement, |
| you could, for example, change the mapping of attribute 0 from black |
| to white. |
| |
| The table below lists attribute and color ranges for various adapter |
| types and screen modes. |
| |
| The VGA uses a different way of calculating color values from the |
| EGA. To calculate a color value, select the intensities of red, green, |
| and blue. The intensity of a color is a number from 0 (low intensity) |
| to 63 (high intensity). Then use the following formula to calculate |
| the actual color number: |
| |
| color number = 65536 * blue + 256 * green + red |
| |
| Because there are gaps in the range of color numbers, you should use |
| the formula rather than just select a number. |
| |
| When used with the IBM Analog Monochrome Monitor, the VGA color values |
| are converted to a gray-scale value by taking a weighted sum of the |
| red, blue, and green intensities: |
| |
| gray value = 11% blue + 59% green + 30% red |
| |
| For example if the blue, green, and red intensities are 45, 20, and |
| 20, the gray value would be .11*45+.59*20+.30*20 or 22 (the fraction |
| in the result is dropped). |
| |
| See the SCREEN statement for the list of colors available for |
| various screen-mode, monitor, and graphics-adapter combinations. |
| |
| |
| Screen Color and Attribute Ranges |
| |
| SCREEN Monitor Adapter Attribute Color |
| Mode Attached Range Range |
| |
| 0 Monochrome MDPA 0-15 N/A |
| Monochrome EGA 0-15 0-2 |
| Color CGA 0-15 N/A |
| Color/Enhanced(b) EGA 0-15 0-63 |
| N/A VGA 0-15 0-63 |
| N/A MCGA 0-15 N/A |
| 1 Color CGA 0-3 N/A |
| Color/Enhanced(b) EGA 0-3 0-15 |
| N/A VGA 0-3 0-15 |
| N/A MCGA 0-3 N/A |
| 2 Color CGA 0-1 N/A |
| Color/Enhanced(b) EGA 0-1 0-15 |
| N/A VGA 0-1 0-15 |
| N/A MCGA 0-1 N/A |
| 7 Color/Enhanced(b) EGA 0-15 0-15 |
| N/A VGA 0-15 0-15 |
| 8 Color/Enhanced(b) EGA 0-15 0-15 |
| N/A VGA 0-15 0-15 |
| 9 Enhanced(b) EGA(c) 0-3 0-63 |
| Enhanced(b) EGA(d) 0-15 0-63 |
| N/A VGA 0-16 0-63 |
| 10 Monochrome EGA 0-3 0-8 |
| N/A VGA 0-3 0-8 |
| 11 N/A VGA 0-1 0-262,143(e) |
| N/A MCGA 0-1 0-262,143(e) |
| 12 N/A VGA 0-15 0-262,143(e) |
| 13 N/A VGA 0-255 0-262,143(e) |
| N/A MCGA 0-255 0-262,143(e) |
| ____________________________________________________________________ |
| N/A = Not Applicable |
| (b) With 64K of EGA memory |
| (c) With more than 64K of EGA memory |
| (d) IBM Enhanced Color Display |
| (e) Display colors are not numbered from 0 to 262,143. See above. |
| |
| Note: Because of their wide range of colors, the VGA and MCGA adapters |
| require a long-integer array in the PALETTE USING statement |
| in screen modes 11 to 13. |
