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POINT

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Samuel Gomes edited this page Nov 8, 2022 · 1 revision

The POINT function returns the pixel COLOR attribute at a specified graphics coordinate or the current graphic cursor position.

Syntax

Color

color_attribute% = POINT (column%, row%)

Graphic cursor position

pointer_coordinate% = POINT({0|1|2|3})

Parameter(s)

Graphic Color syntax:

  • The INTEGER column and row coordinates designate the pixel position color on the screen to read.
  • The return value is an INTEGER palette attribute value or an _UNSIGNED LONG _RGBA 32 bit value in QB64.

Graphic cursor position syntax:

  • The INTEGER position number can be 0 to 3 depending on the cursor position desired:
    • POINT(0) returns the current graphic cursor SCREEN column pixel coordinate.
    • POINT(1) returns the current graphic cursor SCREEN row pixel coordinate.
    • POINT(2) returns the current graphic cursor WINDOW column position.
    • POINT(3) returns the current graphic cursor WINDOW row position.
  • If a WINDOW view port has not been established, the coordinate returned will be the SCREEN cursor pixel position.
  • The return value is the current graphic cursor column or row pixel position on the SCREEN or WINDOW.
  • Graphic cursor positions returned will be the last ones used in a graphic shape such as a CIRCLE center point.

Usage

  • Use _SOURCE first to set the image handle that POINT should read or QB64 will assume the current source image.

_SOURCE 0 'sets POINT to read the current SCREEN image after reading a previous source image

  • POINT cannot be used in SCREEN 0! Use the SCREEN (function) function to point text character codes and colors in SCREEN 0.

POINT in QBasic Legacy Graphic SCREEN Modes:

  • The INTEGER color attributes returned are limited by the number of colors in the legacy SCREEN mode used.
  • Column and row INTEGER parameters denote the graphic pixel coordinate to read.
  • In QB64 the offscreen or off image value returned is -1. Use IF POINT(x, y) <> -1 THEN...
  • In QBasic the coordinates MUST be on the screen or an ERROR Codes will occur.

POINT in QB64 32 Bit Graphic _NEWIMAGE or _LOADIMAGE Modes:

  • Returns _UNSIGNED LONG 32 bit color values. Use _UNSIGNED values when you don't want negative values.
  • _UNSIGNED LONG variables should be used when comparing POINT returns with _RGB or _RGB32 _ALPHA bit values
  • Convert 32 bit color values to RGB intensities(0 to 255) using the _RED32, _GREEN32 and _BLUE32 functions.
  • To convert color intensities to OUT &H3C9 color port palette intensity values divide the values of 0 to 255 by 4.
  • Use the _PALETTECOLOR (function) to convert color port palette intensities in 32 bit modes.

Example(s)

How _RGB 32 bit values return DOUBLE or _UNSIGNED LONG values in QB64.

DIM clr AS LONG 'DO NOT use LONG in older versions of QB64 (V .936 down)
SCREEN _NEWIMAGE(640, 480, 32)
CLS , _RGB(255, 255, 255)  'makes the background opaque white

PRINT "POINT(100, 100) ="; POINT(100, 100)
clr = POINT(100, 100)
PRINT "Variable clr = ";  clr
IF clr = _RGB(255, 255, 255) THEN PRINT "Long OK"
IF POINT(100, 100) = _RGB(255, 255, 255) THEN PRINT "_RGB OK"
IF POINT(100, 100) = clr THEN PRINT "Type OK" 'will not print with a LONG variable type

Note: Change the DIM clr variable type to LONG to see how the last IF statement doesn't PRINT as shown in the output below:


POINT(100, 100) = 4294967295
Variable clr = -1
Long OK
_RGB OK

Using a POINT mouse routine to get the 32 bit color values of an image.

SCREEN _NEWIMAGE(640, 480, 32)
_TITLE "Mouse POINTer 32"

'LINE INPUT "Enter an image file: ", image$  'use quotes around file names with spaces
image$ = "QB64bee.png" 'up to 320 X 240 with current _PUTIMAGE settings
i& = _LOADIMAGE(image$, 32)
IF i& >= -1 THEN BEEP: PRINT "Could NOT load image!": END
w& = _WIDTH(i&): h& = _HEIGHT(i&)

PRINT "Make background transparent?(Y\N)";
BG$ = UCASE$(INPUT$(1))
PRINT BG$
_DELAY 1

'CLS 'commented to keep background alpha 0

IF BG$ = "Y" THEN _CLEARCOLOR _RGB32(255, 255, 255), i& 'make white Background transparent
_PUTIMAGE (320 - w&, 240 - h&)-((2 * w&) + (320 - w&), (2 * h&) + (240 - h&)), i&, 0
_FREEIMAGE i&

_MOUSEMOVE 320, 240 'center mouse pointer on screen

DO: _LIMIT 100
  DO WHILE _MOUSEINPUT
    mx = _MOUSEX
    my = _MOUSEY
    c& = POINT(mx, my)
    r = _RED32(c&)
    g = _GREEN32(c&)
    b = _BLUE32(c&)
    a = _ALPHA32(c&)
    LOCATE 1, 1: PRINT mx; my, "R:"; r, "G:"; g, "B:"; b, "A:"; a; "  "
    LOCATE 2, 2: PRINT "HTML Color: &H" + RIGHT$(HEX$(c&), 6)
  LOOP
LOOP UNTIL INKEY$ > ""
END

Explanation: Use the mouse pointer to get the background RGB of the image to make it transparent with _CLEARCOLOR.

Creating an image mask to PUT an image over other colored backgrounds. See: GET and PUT Demo to run code.

 FOR c = 0 TO 59    '60 X 60 area from 0 pixel
   FOR r = 0 TO 59
    IF POINT(c, r) = 0 THEN PSET (c, r), 15 ELSE PSET (c, r), 0
   NEXT r
 NEXT c
 GET(0, 0)-(60, 60), Image(1500) ' save mask in an array(indexed above original image).

Explanation: In the procedure all black areas(background) are changed to white for a PUT using AND over other colored objects. The other image colors are changed to black for a PUT of the original image using XOR. The array images can be BSAVEd for later use. QB64 can also PUT** a full screen 12 image from an array directly into a** BINARY file.

See Example(s)

See Also

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