BASIC-DOS

BASIC-DOS Graphics Commands

Graphics commands include:

• CIRCLE
• DRAW
• GET
• LINE
• PAINT
• PRESET
• PSET
• PUT

Graphics commands require a color adapter in a graphics mode (see SCREEN). Coordinates are pixels, where (0,0) is the top left corner, x increases to the right (0-319 in SCREEN 1, 0-639 in SCREEN 2), and y increases downward (0-199). Points outside the screen are clipped.

Colors are 0-3 in SCREEN 1 (0 is the background color, and 1-3 come from the current palette; see COLOR), and 0-1 in SCREEN 2. When a color is omitted, the foreground color (3 in SCREEN 1, 1 in SCREEN 2) is used.

BASIC-DOS draws the same pixels as Microsoft BASIC. These features aren’t supported yet: STEP (relative) coordinates, the POINT function, DRAW’s A, TA, X, and “=variable” commands, and GET/PUT with floating-point arrays.

SCREEN 1
LINE (0,0)-(319,199),3,B
CIRCLE (160,100),60,1
PAINT (160,100),2,1

CIRCLE

CIRCLE (x,y),r[,[color][,[start][,[end][,aspect]]]]

Draws a circle (or ellipse) with radius r, or an arc from the start angle to the end angle (in radians, from 0 to 2pi), with lines to the center for negative angles. If *aspect (the ratio of the y radius to the x radius) is omitted, the circle looks round on a standard display.

DRAW

DRAW string

Draws lines from the last point, using these commands:

• U, D, L, R [n]: move up, down, left, or right n points (default 1)
• E, F, G, H [n]: move diagonally up and right, down and right, down and left, or up and left
• M x,y: move to x,y (or relative to the last point, if x begins with + or -)
• B: prefix; move without drawing
• N: prefix; draw without moving
• C n: set the color
• S n: set the scale, in quarters (eg, S8 doubles all distances); the default is 4

Example:

DRAW "C1 U20 R20 D20 L20 BM+30,0 E10 F10 L20"

GET

GET (x1,y1)-(x2,y2),array

Stores the pixels of the specified rectangle in an integer array (eg, DIM A%(100)), so that they can be drawn later with PUT. The image format is the same as Microsoft BASIC’s: two 16-bit words containing the width (in bits) and height, followed by the pixel rows, packed into bytes, with each row starting on a byte boundary. Each array element holds one 16-bit word.

LINE

LINE [(x1,y1)]-(x2,y2)[,[color][,B

BF]]

Draws a line from (x1,y1) to (x2,y2), or with B, a box with those corners, or with BF, a filled box. If the first point is omitted, the last point drawn is used.

PAINT

PAINT (x,y)[,[paint][,border]]

Fills the area around (x,y) with the paint color, up to the border color (which defaults to the paint color). Like Microsoft BASIC, PAINT also fills through pixels that already have the paint color.

PRESET

PRESET (x,y)[,color]

Same as PSET, except that the default color is the background color (0).

PSET

PSET (x,y)[,color]

Draws a point, using the foreground color if no color is specified.

PUT

PUT (x,y),array[,PSET

PRESET

XOR

OR

AND]

Draws an image stored by GET with its top left corner at (x,y), combining it with the screen using XOR, unless another action is specified:

• PSET: draws the image as-is
• PRESET: draws the inverse of the image
• XOR: inverts the screen wherever the image has pixels set (so a second PUT restores the screen)
• OR: adds the image to the screen
• AND: keeps only the screen pixels that the image also has set

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