_COPYIMAGE - QB64 Wiki

_COPYIMAGE

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The _COPYIMAGE function creates an identical designated image in memory with a different negative LONG handle value.


Syntax:

newhandle& = _COPYIMAGE[(imageHandle&[, mode%)]]


Parameters:

  • The LONG newhandle value returned will be different than the source handle value supplied.
  • If imagehandle parameter is omitted or zero is designated, the current software destination screen or image is copied.
  • If 1 is designated instead of an imagehandle, it designates the last GL hardware surface to copy.
  • Mode 32 can be used to convert 256 color images to 32 bit colors.
  • Mode 33 images are hardware accelerated in GL, and are created using _LOADIMAGE or _COPYIMAGE. (_NEWIMAGE later)


Usage:

  • The function copies any image or screen handle to a new and unique negative LONG handle value.
  • Valid copy handles are less than -1. Invalid handles return -1 or 0 if it was never created.
  • Every attribute of the passed image or program screen is copied to a new handle value in memory.
  • 32 bit screen surface backgrounds(black) have zero _ALPHA so that they are transparent when placed over other surfaces.
Use CLS or _DONTBLEND to make a new surface background _ALPHA 255 or opague.
  • Images are not deallocated when the SUB or FUNCTION they are created in ends. Free them with _FREEIMAGE.
  • It is IMPORTANT to free discarded images with _FREEIMAGE to prevent PC memory allocation errors!
  • Do NOT try to free image handles currently being used as the active SCREEN! Change screen modes first.


Example: Restoring a Legacy SCREEN using the _COPYIMAGE return value.

SCREEN 13 CIRCLE (160, 100), 100, 40 DO: SLEEP: LOOP UNTIL INKEY$ <> "" 'backup screen before changing SCREEN mode oldmode& = _COPYIMAGE(0) 'the 0 value designates the current destination SCREEN s& = _NEWIMAGE(800, 600, 32) SCREEN s& LINE (100, 100)-(500, 500), _RGB(0, 255, 255), BF DO: SLEEP: LOOP UNTIL INKEY$ <> "" SCREEN oldmode& 'restore original screen IF s& < -1 THEN _FREEIMAGE s& END

Note: Only free valid handle values with _FREEIMAGE AFTER a new SCREEN mode is being used by the program.


Example 2: QB64 GL program copies desktop to a hardware image to form a 3D triangle:

SCREEN _NEWIMAGE(640, 480, 32) my_hardware_handle = _COPYIMAGE(_SCREENIMAGE, 33) 'take a screenshot and use it as our texture _MAPTRIANGLE (0, 0)-(500, 0)-(250, 500), my_hardware_handle TO_ (-1, 0, -1)-(1, 0, -1)-(0, 5, -10), , _SMOOTH _DISPLAY DO: _LIMIT 30: LOOP UNTIL INKEY$ <> ""

Code courtesy of Galleon
Example 2 PNG image


See also:



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