forked from Galleondragon/qb64
PSET
Cory Smith edited this page Sep 1, 2022
·
7 revisions
The PSET graphics SCREEN (statement) statement sets a pixel to a coordinate with a default or designated color attribute.
PSET [STEP](column%, row%)[, colorAttribute]
- 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 _DEST page's _DEFAULTCOLOR.
- Color attributes are limited to the SCREEN mode used. Any color value other than 0 will be white in SCREEN (statement)s 2 or 11.
- PSET can locate other graphics objects and color DRAW statements.
- The PSET action can be used in a graphics PUT (graphics statement) 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.)
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.
Magnifying a box portion of a Mandelbrot image with PSET
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
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.