glPixelZoom(3G)		       OpenGL Reference		       glPixelZoom(3G)

NAME    [Toc]    [Back]

     glPixelZoom - specify the pixel zoom factors

C SPECIFICATION    [Toc]    [Back]

     void glPixelZoom( GLfloat xfactor,
		       GLfloat yfactor )

PARAMETERS    [Toc]    [Back]

     xfactor, yfactor Specify the x and	y zoom factors for pixel write
		      operations.

DESCRIPTION    [Toc]    [Back]

     glPixelZoom specifies values for the x and	y zoom factors.	 During	the
     execution of glDrawPixels or glCopyPixels,	if (xr,	yr) is the current
     raster position, and a given element is in	the mth	row and	nth column of
     the pixel rectangle, then pixels whose centers are	in the rectangle with
     corners at

				.		.
			 (xr + n xfactor, yr + m yfactor)

				.		    .
		     (xr + (n+1) xfactor, yr + (m+1) yfactor)

     are candidates for	replacement.  Any pixel	whose center lies on the
     bottom or left edge of this rectangular region is also modified.

     Pixel zoom	factors	are not	limited	to positive values.  Negative zoom
     factors reflect the resulting image about the current raster position.

ERRORS    [Toc]    [Back]

     GL_INVALID_OPERATION is generated if glPixelZoom is executed between the
     execution of glBegin and the corresponding	execution of glEnd.

ASSOCIATED GETS    [Toc]    [Back]

     glGet with	argument GL_ZOOM_X
     glGet with	argument GL_ZOOM_Y
     glGet with	argument GL_INTERLACE_SGIX


MACHINE	DEPENDENCIES
     The SGIX_interlace	extension is supported only on InfiniteReality
     systems, on RealityEngine,	RealityEngine2,	and VTX	systems, on Octane2
     VPro systems, and on O2 systems.

     On	InfiniteReality	systems, the absolute values of	the zoom factors must
     be	strictly less than 128.	 If not, they are clamped and GL_INVALID_VALUE
     is	generated.

     Pixel zoom	factors	are snapped to fixed point precision on	O2 systems,
     Indy and XL systems, XS, XZ, Elan,	and Extreme systems.  glGet will
     return these values.



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glPixelZoom(3G)		       OpenGL Reference		       glPixelZoom(3G)

SEE ALSO    [Toc]    [Back]

     glCopyPixels, glEnable, glDrawPixels.


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