GET (graphics statement) - QB64 Wiki

GET (graphics statement)

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The GET statement is used in graphics to store a box area image of the screen into an INTEGER array.


Syntax:

GET [STEP] (column1, row1)-[STEP](column2, row2), Array([index])[, offscreen_color]


Parameters:

  • Column and row INTEGER coordinates for the box area must be on the screen except when using an offscreen color.
  • INTEGER Array sizes must be large enough (use width * height of the box area + 4) to hold the data or an error will occur!
  • The array index offset is optional. If the offset is zero the brackets may be empty (Qbasic does not require the brackets).
  • The off screen color pixels will be returned as the designated color when part of an image is off screen in QB64 only.


Usage:

  • The STEP keyword can be used to for coordinates relative to the last graphic coordinates used.
  • A graphic screen mode MUST be used! See the SCREEN statement for graphic screen dimensions.
  • QB64 GET statements can use coordinates off of the screen when an off screen color is designated. STEP can be used for relative coordinates.
  • The GET box coordinates are set just like a LINE box statement is placed. You can use a box to find the correct GET area.
  • Once GET has placed the pixel image data in the array, PUT the image or BSAVE it to a file.
  • Once the image is stored in an array PUT can be used to place the image on the screen.
  • SCREEN 12 can only GET 1/3 of a full SCREEN 12 image (QB64 can save entire screen). Rows would increment 160 each GET.
  • A _SOURCE handle can be set to GET image areas other than the ones on the current screen. Use _DEST to PUT images there.
  • To GET more than one image to the same array, designate an offset index that is not being used and is large enough to hold the data.
  • The INTEGER array size can be calculated as slightly larger than the box area width times the height. A closer estimate can be done by reading the array indices from UBOUND to LBOUND after a GET of a white box area. In QB64 a LONG array can be used for large or full screen images.
  • RGB color settings can be embedded at the beginning of the array for transferring custom colors. Index the GET image data after the settings.
  • In QB64 _PUTIMAGE is recommended over PUT as it can also do the GET directly from the image source without requiring an array.
  • PUT and GET file statements can also write and read image array data using BINARY files instead of using BSAVE or BLOAD.


Example 1: How to use GET and PUT to move a sprite with the arrow keys.

DEFINT A-Z DIM BG(300), Box(300), SC(127) ' BG holds background images. Box holds the Box image. SCREEN 13 ' graphic coordinate minimums are 0 to 319 column or 199 row maximums. ' set up screen background COLOR 4: LOCATE 10, 5: PRINT "Multikey Keyboard input routine" COLOR 10: LOCATE 12, 4: PRINT "Use the arrow keys to move the box." LOCATE 13, 4: PRINT "Note that you can press two or more" LOCATE 14, 4: PRINT "keys at once for diagonal movement!" COLOR 14: LOCATE 16, 4: PRINT " Also demonstrates how GET and PUT " LOCATE 17, 4: PRINT "are used to preserve the background." COLOR 11: LOCATE 20, 11: PRINT "Press [Esc] to quit" x = 150: y = 50: PX = x: PY = y ' actual box starting position GET (x, y)-(x + 15, y + 15), BG ' GET original BG at start box position LINE (x, y)-(x + 15, y + 15), 9, BF ' the plain blue box to move GET (x, y)-(x + 15, y + 15), Box ' GET to Box Array DO 'main loop t! = TIMER + .05 DO ' 1 Tick (1/18th second) keypress scancode read loop a$ = INKEY$ ' So the keyboard buffer won't get full code% = INP(&H60) ' Get keyboard scan code from port 96 IF code% < 128 THEN SC(code%) = 1 ELSE SC(code% - 128) = 0 'true/false values to array LOOP UNTIL TIMER > t!' loop until one tick has passed PX = x: PY = y ' previous coordinates IF SC(75) = 1 THEN x = x - 5: IF x < 0 THEN x = 0 IF SC(77) = 1 THEN x = x + 5: IF x > 304 THEN x = 304 IF SC(72) = 1 THEN y = y - 5: IF y < 0 THEN y = 0 IF SC(80) = 1 THEN y = y + 5: IF y > 184 THEN y = 184 IF x <> PX OR y <> PY THEN ' look for a changed coordinate value WAIT 936, 8: PUT(PX, PY), BG, PSET ' replace previous BG first GET (x, y)-(x + 15, y + 15), BG ' GET BG at new position before box is set PUT(x, y), Box, PSET ' PUT box image at new position END IF LOOP UNTIL SC(1) = 1 ' main loop until [Esc] key (scan code 1) is pressed


Example 2: How to GET graphics from an image other than the present screen using _SOURCE and _DESTination.

DIM img(20 * 20 + 4) AS INTEGER 'create img% array to hold 20 by 20 image data a& = _NEWIMAGE(800, 600, 13) 'larger surface a& emulates screen 13 colors & resolution SCREEN 13 'program screen 13 _DEST a& 'set desination as the image page a& CIRCLE (700, 300), 10, 10 'draw green circle on image page _SOURCE a& 'set source as image page a& GET (690, 290)-(710, 310), img() 'GET a square screen area similar to a LINE Box. _DEST 0 'set destination as the program screen PUT (100, 100), img() 'PUT the Top Left Corner of box area to pixel 100, 100

Notes: A _LOADIMAGE handle could also be used as a source to GET a portion or all of an image file.


See also:



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