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dmFXDrawPixels(3dm)					   dmFXDrawPixels(3dm)

NAME    [Toc]    [Back]

     dmFXDrawPixels, dmFXConvolve, dmFXScaleBias, dmFXMatrixMultiply - pixel
     transfer operations for special effects

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/fx_buffer.h>

     DMstatus dmFXDrawPixels    [Toc]    [Back]
	   ( PRX_ScanlineBuffer	destination,
	     int xPosition,
	     int yPosition,
	     PRX_ScanlineBuffer	source,
	     int xOffset,
	     int yOffset,
	     int width,
	     int height	)

     DMstatus dmFXConvolve    [Toc]    [Back]
	   ( PRX_ScanlineBuffer	destination,
	     PRX_ScanlineBuffer	source,
	     int matrixWidth,
	     int matrixHeight,
	     const GLfloat* matrix,
	     const GLfloat bias,
	     const GLfloat scale )

     DMstatus dmFXScaleBias    [Toc]    [Back]
	   ( PRX_ScanlineBuffer	destination,
	     PRX_ScanlineBuffer	source,
	     const GLfloat redScale,
	     const GLfloat redBias,
	     const GLfloat greenScale,
	     const GLfloat greenBias,
	     const GLfloat blueScale,
	     const GLfloat blueBias,
	     const GLfloat alphaScale,
	     const GLfloat alphaBias )

     DMstatus dmFXMatrixMultiply    [Toc]    [Back]
	   ( PRX_ScanlineBuffer	destination,
	     PRX_ScanlineBuffer	source,
	     const GLfloat* matrix,
	     const GLfloat bias,
	     const GLfloat scale )

PARAMETERS    [Toc]    [Back]

     These two parameters are common to	all of these functions.	 The other
     parameters	are described below in the sections on the different

									Page 1

dmFXDrawPixels(3dm)					   dmFXDrawPixels(3dm)

     destination   The image buffer into which pixels are copied.

     source	   The image buffer from which pixels are copied.

DESCRIPTION    [Toc]    [Back]

     All of these functions copy pixels	from one image buffer to another.
     They make it easy to do common image processing operations	without	having
     to	set up all of the proper OpenGL	state. They also correctly compensate
     for the fact that video images are	stored top-to-bottom in	memory,
     instead of	the usual OpenGL bottom-to-top orientation.

     All these routines	assume that the	destination buffer has the standard
     coordinate	system that is set up by dmFXSetupOutputImageBuffer, with
     (0,0) at the lower-left, and (width,height) at the	upper-right.

     GL_UNPACK_SKIP_PIXELS, and	GL_UNPACK_ALIGNMENT may	all be changed by
     these functions.

     dmFXDrawPixels copies a rectangular block of pixels from the source to
     the destination, unmodified.  xPosition and yPosition are the coordinates
     of	the lower-left corner of the rectangle in the destination where	the
     pixel will	be placed. Any rectangular portion of the source buffer	can be
     copied.  The rectangle is specified by xOffset and	yOffset	(the lowerleft
 corner), and width and height.

     dmFXConvolve copies the entire source buffer to the destination, applying
     an	arbitrary 2D convolution matrix, matrix.  The size of the matrix is
     specified by matrixWidth and matrixHeight,	and matrix points to a 2-
     dimensional array of coefficients indexed with coordinates	i,j such that
     i increases from left to right and	j increases from bottom	to top.	The
     same convolution matrix is	applied	equally	to the R, G, B,	and A
     components	of each	pixel.	After each component of	each pixel is computed
     (by the matrix multiplication), it	is multiplied by scale and offset by
     bias. The resulting pixel values are clamped to the range from 0.0	to
     1.0.  If the matrix size given exceeds the	maximum	allowed	by OpenGL,
     DM_FAILURE	is returned, and the error code	is set to

     dmFXScaleBias copies the entire source buffer to the destination,
     applying a	color correction.  Each	component of each pixel	is multiplied
     by	a scale	(redScale, greenScale, blueScale, or alphaScale) and the
     offset by a bias (redBias,	greenBias, blueBias, or	alphaBias).  The
     resulting values are clamped to the range from 0.0	to 1.0.

     dmFXMatrixMultiply	performs a more	general	color correction than
     dmFXScaleBias.  The four components of each pixel are treated as a	4-
     element vector and	multiplied by a	4x4 matrix (matrix) to produce new
     values for	the four components, then the resulting	components are each
     multiplied	by scale and offset by bias:

									Page 2

dmFXDrawPixels(3dm)					   dmFXDrawPixels(3dm)

	 R' = ((m1 * R)	+ (m5 *	G) +  (m9 * B) + (m13 *	A)) * Rscale + Rbias
	 G' = ((m2 * R)	+ (m6 *	G) + (m10 * B) + (m14 *	A)) * Gscale + Gbias
	 B' = ((m3 * R)	+ (m7 *	G) + (m11 * B) + (m15 *	A)) * Bscale + Bbias
	 A' = ((m4 * R)	+ (m8 *	G) + (m12 * B) + (m16 *	A)) * Ascale + Abias

     Finally, each component is	clamped	to the range from 0.0 to 1.0.

PIXEL ZOOM    [Toc]    [Back]

     The functions all assume that the modelview matrix	has been set up	so
     that the coordinate system	for the	full output image has (0,0) at the
     lower-left	corner and (width,height) at the upper-right corner.  They
     also assume that the screen coordinates are the same.  In other words,
     they assume that the pixel	zoom (see glPixelZoom) has been	set so that
     using glDrawPixels	to draw	a full-sized image at (0,0) will exactly fill
     the render	area with the image.  If (0,0) is at the upper-left of the
     viewport, then the	Y pixel	zoom should be negative.

     During preview, applications may be rendering the results of plug-ins
     directly to the screen, and may not be rendering full-size.  This is
     allowed as	long as	the pixel zoom is set to meet the above	criteria.

     IMPORTANT:	It is highly recommended that plug-in authors use these
     functions whenever	doing pixel-oriented operations, because they
     correctly handle drawing images upside-down and they correctly handle
     pixel zoom.

SEE ALSO    [Toc]    [Back]

     dmFXSetupInputImageBuffer(3dm), dmFXSetupScanlineBuffer(3dm),
     dmFXIsGLExtensionSupported(3dm), dmGetError(3dm).

									PPPPaaaaggggeeee 3333
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