_NEWIMAGE - QB64 Wiki

_NEWIMAGE

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The _NEWIMAGE function prepares a window image surface and returns the LONG handle value.


Contents

Syntax

handle& = _NEWIMAGE(width&, height&[, {0|1|2|7|8|9|10|11|12|13|256|32}])


Parameters

  • Minimum LONG screen dimensions are width& >= 1, height& >= 1 measured in pixels as INTEGER or LONG values.
    • For mode 0 (text), width& and height& are measured in character blocks, not pixels.
  • Mode is either a QBasic type screen mode (0 to 2 or 7 to 13), 256 colors or 32 bit (16 million colors) compatible.


Description

  • If the mode is omitted, an image will be created with the same BPP mode, font (which may block freeing of that font), palette, selected colors, transparent color, blend state and print method settings as the current _DESTination image/screen page.
  • Valid LONG handle returns are less than -1. Invalid handles equal -1 and a zero or positive value is also invalid.
  • You can create any sized window (limited by the OS) in any emulated SCREEN mode or 32 bit using this function.
  • Default text block size in emulated SCREEN modes 1, 2, 7, 8 and 13 is 8 X 8; 9 and 10 is 8 X 14; 11, 12, 256 and 32 bit is 8 X 16. The text block pixel size will allow you to calculate the available text rows and columns in a custom sized screen.
  • To view the image page, just use SCREEN handle&. Even if another procedure changes the screen mode and clears the screen, the image can be restored later by using the same SCREEN handle mode.
  • Use the _COPYIMAGE function to preserve a SCREEN handle value when changing to another screen mode to restore it later.
  • 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 unused or uneeded images with _FREEIMAGE to prevent CPU memory overflow errors.
  • Do not try to free image handles currently being used as the active SCREEN. Change screen modes first.


Examples

Example 1: Shrinking a SCREEN 0 text window's size:

SCREEN _NEWIMAGE(28, 25, 0)


Example 2: Creating an 800 by 600 window version of SCREEN 12 with 256 colors (text 37 X 100):

handle& = _NEWIMAGE(800, 600, 256) SCREEN handle&


Example 3: Setting up a 32 bit SCREEN with _NEWIMAGE for page flipping in QB64.

SCREEN _NEWIMAGE(640, 480, 32), , 1, 0

Note: _DISPLAY may be used as a substitute for page flipping or PCOPY.


Example 4: Switching between two different SCREEN modes

_TITLE "Switching SCREEN modes" SCREEN _NEWIMAGE (800, 600, 256) mode1& = _DEST 'get current screen mode handle mode2& = _NEWIMAGE (300, 200, 13) _DEST mode2& 'prepare small window COLOR 10: LOCATE 10, 13: PRINT "mode2& = "; mode2& COLOR 13: LOCATE 16, 16: PRINT "First" _DEST mode1& 'work in main window LOCATE 5 FOR c = 1 TO 248 Color c: PRINT c; NEXT COLOR 12: LOCATE 20, 44: PRINT "mode1& = "; mode1& COLOR 11: LOCATE 30, 34: PRINT "Press a key to goto Pop-up Window" DO: SLEEP: LOOP UNTIL INKEY$ <> "" SCREEN mode2& 'switch to small window DO: SLEEP: LOOP UNTIL INKEY$ <> "" SCREEN mode1& 'back to main window COLOR 12: LOCATE 37, 43: PRINT "One more time!" DO: SLEEP: LOOP UNTIL INKEY$ <> "" SCREEN mode2& 'back to small window COLOR 14: LOCATE 16, 16: PRINT "LAST "

Explanation: The _DEST function can determine the present screen mode destination handle. The second _NEWIMAGE handle is created using a SCREEN 13 palette(256 colors also). Each SCREEN is worked on after changing the destination with _DEST handle& statement. Images can be created before viewing them. When a key is pressed the second SCREEN created is displayed and so on.
Legacy SCREEN modes can also return a _DEST value, but the value will create a handle error. To restore legacy screens get the_COPYIMAGE function value before changing screens. Then restore it using SCREEN oldmode&.


More examples


See also



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