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PSET

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The PSET grahics SCREEN statement sets a pixel to a coordinate with a default or designated color attribute.


Contents

Syntax

PSET [STEP](column%, row%)[, colorAttribute]


Parameters:

  • Can use STEP relative graphics coordinates from a previous graphic object.
  • Column and row can be literal or variable INTEGER coordinates values which can be offscreen.
  • If the colorAttribute is omitted, PSET will use the current destination page's _DEFAULTCOLOR.


Usage:

  • Color attributes are limited to the SCREEN mode used. Any color value other than 0 will be white in SCREENs 2 or 11.
  • PSET can locate other graphics objects and color DRAW statements.
  • The PSET action can be used in a graphics PUT to produce an identical image on any background.
  • The graphic cursor is set to the center of the program window on program start for STEP relative coordinates.
  • PSET can be used in any graphic screen mode, but cannot be used in the default screen mode 0 as it is text only! (Or in any _NEWIMAGE(x, y, 0) screens which are text only as well.)


Example: Using PSET to locate and color a DRAW statement.

SCREEN 12 PSET(100, 100), 12 DRAW "U20 R20 D20 L20"

Screen results: A drawn box that is bright red.


Example 2: Magnifying a box portion of a Mandelbrot image with PSET

DECLARE SUB readmouse (x AS INTEGER, y AS INTEGER, z AS INTEGER) DECLARE SUB rectangle (x1 AS INTEGER, y1 AS INTEGER, x2 AS INTEGER, y2 AS INTEGER) DECLARE FUNCTION mandel% (x AS DOUBLE, y AS DOUBLE, limit AS INTEGER) DECLARE SUB drawmand (x AS DOUBLE, y AS DOUBLE, mag AS DOUBLE) DEFSTR A-Z DIM red(15) AS INTEGER, green(15) AS INTEGER, blue(15) AS INTEGER DIM i AS INTEGER SCREEN 12 FOR i = 0 TO 15: READ red(i): NEXT FOR i = 0 TO 15: READ green(i): NEXT FOR i = 0 TO 15: READ blue(i): NEXT FOR i = 0 TO 15: PALETTE i, 65536 * blue(i) + 256& * green(i) + red(i): NEXT DATA 0,63,63,63,63,63,31, 0, 0,31,31,31,47,63,63,63 DATA 0, 0,15,31,47,63,63,63,63,31,15, 0, 0, 0, 0, 0 DATA 0, 0, 0, 0, 0, 0, 0, 0,31,63,63,63,63,63,42,21 DIM dmag AS INTEGER, dlogmag AS INTEGER DIM a AS DOUBLE, b AS DOUBLE, mag AS DOUBLE DIM dx AS INTEGER, dy AS INTEGER DIM mx AS INTEGER, my AS INTEGER, mz AS INTEGER dmag = 16 mag = 1 a = -.75 b = 0 DO DIM limitx AS DOUBLE, limit AS INTEGER DIM inc AS DOUBLE, left AS DOUBLE, top AS DOUBLE limitx = 150 * (LOG(mag) + 1) IF limitx > 32767 THEN limitx = 32767 limit = INT(limitx) inc = .004 / mag left = a - inc * 319 top = b + inc * 239 CLS DIM yy AS INTEGER, xx AS INTEGER DIM x AS DOUBLE, y AS DOUBLE, z AS INTEGER FOR yy = 0 TO 479 y = top - inc * yy FOR xx = 0 TO 639 x = left + inc * xx z = mandel(x, y, limit) IF z < limit THEN PSET (xx, yy), 1 + z MOD 15 IF INKEY$ = CHR$(27) THEN SYSTEM NEXT NEXT mz = 0 CALL readmouse(mx, my, mz) DO dx = 319 \ dmag dy = 239 \ dmag CALL readmouse(mx, my, mz) IF mz THEN EXIT DO CALL rectangle(mx - dx, my - dy, mx + dx, my + dy) DIM t AS DOUBLE t = TIMER WHILE t = TIMER key$ = INKEY$ SELECT CASE key$ CASE CHR$(27) SYSTEM CASE CHR$(0) + CHR$(72) dmag = dmag \ 2 IF dmag < 2 THEN dmag = 2 CASE CHR$(0) + CHR$(80) dmag = dmag * 2 IF dmag > 128 THEN dmag = 128 END SELECT WEND CALL rectangle(mx - dx, my - dy, mx + dx, my + dy) LOOP a = a + inc * (mx - 319): b = b - inc * (my - 239) IF (mz = 1) THEN mag = dmag * mag ELSE mag = mag / dmag IF (mag < 1) THEN mag = 1 LOOP FUNCTION mandel% (x AS DOUBLE, y AS DOUBLE, limit AS INTEGER) DIM a AS DOUBLE, b AS DOUBLE, t AS DOUBLE DIM n AS INTEGER n = 0: a = 0: b = 0 DO t = a * a - b * b + x b = 2 * a * b + y: a = t n = n + 1 LOOP UNTIL a * a + b * b > 4 OR n > limit mandel = n END FUNCTION SUB readmouse (x AS INTEGER, y AS INTEGER, z AS INTEGER) z=0 DO if _MOUSEBUTTON(1) THEN z = z OR 1 if _MOUSEBUTTON(2) THEN z = z OR 2 if _MOUSEBUTTON(3) THEN z = z OR 4 LOOP UNTIL _MOUSEINPUT=0 x=_MOUSEX y=_MOUSEY END SUB SUB rectangle (x1 AS INTEGER, y1 AS INTEGER, x2 AS INTEGER, y2 AS INTEGER) DIM i AS INTEGER, j AS INTEGER FOR i = x1 TO x2 j = POINT(i, y1) PSET (i, y1), j XOR 15 j = POINT(i, y2) PSET (i, y2), j XOR 15 NEXT FOR i = y1 TO y2 j = POINT(x1, i) PSET (x1, i), j XOR 15 j = POINT(x2, i) PSET (x2, i), j XOR 15 NEXT END SUB

Code by Codeguy
Notes: Left click, to zoom in on the rectangle. Right click, to zoom out. Up arrow makes the rectangle bigger and down arrow makes the rectangle smaller.


See also:



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