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<HTML><BODY><PRE>     <STRONG>NAME</STRONG>	  <STRONG>fglCopyPixels</STRONG>	- copy pixels in the frame buffer     <STRONG>FORTRAN</STRONG> <STRONG>SPECIFICATION</STRONG>	  SUBROUTINE <STRONG>fglCopyPixels</STRONG>( INTEGER*4 <EM>x</EM>,				    INTEGER*4 <EM>y</EM>,				    INTEGER*4 <EM>width</EM>,				    INTEGER*4 <EM>height</EM>,				    INTEGER*4 <EM>type</EM> )     <STRONG>PARAMETERS</STRONG>	  <EM>x</EM>, <EM>y</EM> Specify the window coordinates of the lower left	corner	       of the rectangular region of pixels to be copied.	  <EM>width</EM>, <EM>height</EM>	       Specify the dimensions of the rectangular region	of	       pixels to be copied.  Both must be nonnegative.	  <EM>type</EM> Specifies whether color values, depth values, or	       stencil values are to be	copied.	 Symbolic constants	       <STRONG>GL_COLOR</STRONG>, <STRONG>GL_DEPTH</STRONG>, and <STRONG>GL_STENCIL</STRONG> are accepted.     <STRONG>DESCRIPTION</STRONG>	  <STRONG>fglCopyPixels</STRONG>	copies a screen-aligned	rectangle of pixels	  from the specified frame buffer location to a	region	  relative to the current raster position.  Its	operation is	  well defined only if the entire pixel	source region is	  within the exposed portion of	the window.  Results of	copies	  from outside the window, or from regions of the window that	  are not exposed, are hardware	dependent and undefined.	  <EM>x</EM> and	<EM>y</EM> specify the window coordinates of the	lower left	  corner of the	rectangular region to be copied.  <EM>width</EM>	and	  <EM>height</EM> specify the dimensions	of the rectangular region to	  be copied.  Both <EM>width</EM> and <EM>height</EM> must not be	negative.	  Several parameters control the processing of the pixel data	  while	it is being copied.  These parameters are set with	  three	commands:  <STRONG>fglPixelTransfer</STRONG>, <STRONG>fglPixelMap</STRONG>, and	  <STRONG>fglPixelZoom</STRONG>.	 This reference	page describes the effects on	  <STRONG>fglCopyPixels</STRONG>	of most, but not all, of the parameters	  specified by these three commands.	  <STRONG>fglCopyPixels</STRONG>	copies values from each	pixel with the lower	  left-hand corner at (<EM>x</EM> + i, <EM>y</EM>	+ j) for 0<EM>&lt;</EM>i&lt;<EM>width</EM>  and	  0<EM>&lt;</EM>j&lt;<EM>height</EM>.  This pixel is said to be	the ith	pixel in the	  jth row. Pixels are copied in	row order from the lowest to	  the highest row, left	to right in each row.	  <EM>type</EM> specifies whether color,	depth, or stencil data is to	  be copied.  The details of the transfer for each data	type	  are as follows:	  <STRONG>GL_COLOR</STRONG>	 Indices or RGBA colors	are read from the			 buffer	currently specified as the read	source			 buffer	(see <STRONG>fglReadBuffer</STRONG>).  If the GL	is in			 color index mode, each	index that is read			 from this buffer is converted to a fixed-			 point format with an unspecified number of			 bits to the right of the binary point.	 Each			 index is then shifted left by <STRONG>GL_INDEX_SHIFT</STRONG>			 bits, and added to <STRONG>GL_INDEX_OFFSET</STRONG>.  If			 <STRONG>GL_INDEX_SHIFT</STRONG>	is negative, the shift is to			 the right.  In	either case, zero bits fill			 otherwise unspecified bit locations in	the			 result.  If <STRONG>GL_MAP_COLOR</STRONG> is true, the index			 is replaced with the value that it references			 in lookup table <STRONG>GL_PIXEL_MAP_I_TO_I</STRONG>.  Whether			 the lookup replacement	of the index is	done			 or not, the integer part of the index is then			 ANDed with 2b-1, where	b is the number	of			 bits in a color index buffer.			 If the	GL is in RGBA mode, the	red, green,			 blue, and alpha components of each pixel that			 is read are converted to an internal			 floating-point	format with unspecified			 precision.  The conversion maps the largest			 representable component value to 1.0, and			 component value 0 to 0.0.  The	resulting			 floating-point	color values are then			 multiplied by <STRONG>GL_c_SCALE</STRONG> and added to			 <STRONG>GL_c_BIAS</STRONG>, where <EM>c</EM> is RED, GREEN, BLUE, and			 ALPHA for the respective color	components.			 The results are clamped to the	range [0,1].			 If <STRONG>GL_MAP_COLOR</STRONG> is true, each color component			 is scaled by the size of lookup table			 <STRONG>GL_PIXEL_MAP_c_TO_c</STRONG>, then replaced by the			 value that it references in that table.  <EM>c</EM> is			 R, G, B, or A.			 The GL	then converts the resulting indices or			 RGBA colors to	fragments by attaching the			 current raster	position <EM>z</EM> coordinate and			 texture coordinates to	each pixel, then			 assigning window coordinates (x +i,y +j),			 where (x ,y ) is the current ra<STRONG>s</STRONG>ter <STRONG>p</STRONG>osition,			 and the <STRONG>p</STRONG>ix<STRONG>e</STRONG>l was the ith pixel in the	jth			 row.  These pixel fragments are then treated			 just like the fragments generated by			 rasterizing points, lines, or polygons.			 Texture mapping, fog, and all the fragment			 operations are	applied	before the fragments			 are written to	the frame buffer.	  <STRONG>GL_DEPTH</STRONG>	 Depth values are read from the	depth buffer			 and converted directly	to an internal			 floating-point	format with unspecified			 precision.  The resulting floating-point			 depth value is	then multiplied	by			 <STRONG>GL_DEPTH_SCALE</STRONG>	and added to <STRONG>GL_DEPTH_BIAS</STRONG>.			 The result is clamped to the range [0,1].			 The GL	then converts the resulting depth			 components to fragments by attaching the			 current raster	position color or color	index			 and texture coordinates to each pixel,	then			 assigning window coordinates (x +i,y +j),			 where (x ,y ) is the current ra<STRONG>s</STRONG>ter <STRONG>p</STRONG>osition,			 and the <STRONG>p</STRONG>ix<STRONG>e</STRONG>l was the ith pixel in the	jth			 row.  These pixel fragments are then treated			 just like the fragments generated by			 rasterizing points, lines, or polygons.			 Texture mapping, fog, and all the fragment			 operations are	applied	before the fragments			 are written to	the frame buffer.	  <STRONG>GL_STENCIL</STRONG>	 Stencil indices are read from the stencil			 buffer	and converted to an internal fixed-			 point format with an unspecified number of			 bits to the right of the binary point.	 Each			 fixed-point index is then shifted left	by			 <STRONG>GL_INDEX_SHIFT</STRONG>	bits, and added	to			 <STRONG>GL_INDEX_OFFSET</STRONG>.  If <STRONG>GL_INDEX_SHIFT</STRONG> is			 negative, the shift is	to the right.  In			 either	case, zero bits	fill otherwise			 unspecified bit locations in the result.  If			 <STRONG>GL_MAP_STENCIL</STRONG>	is true, the index is replaced			 with the value	that it	references in lookup			 table <STRONG>GL_PIXEL_MAP_S_TO_S</STRONG>.  Whether the			 lookup	replacement of the index is done or			 not, the integer part of the index is then			 ANDed with 2b-1, where	b is the number	of			 bits in the stencil buffer.  The resulting			 stencil indices are then written to the			 stencil buffer	such that the index read from			 the ith location of the jth row is written to			 location (x +i,y +j), where (x	,y ) is	the			 current ras<STRONG>t</STRONG>er	p<STRONG>o</STRONG>sition.  Onlyrth<STRONG>e</STRONG> pixel			 ownership test, the scissor test, and the			 stencil writemask affect these	write			 operations.	  The rasterization described thus far assumes pixel zoom	  factors of 1.0.  If	  <STRONG>fglPixelZoom</STRONG> is used to change the x and y pixel zoom	  factors, pixels are converted	to fragments as	follows.  If	  (x , y ) is the current raster position, and a given pixel	  isrin	<STRONG>t</STRONG>he ith	location in the	jth row	of the source pixel	  rectangle, then fragments are	generated for pixels whose	  centers are in the rectangle with corners at			     (x	+zoom i, y +zoom j)			       r     x	  r	y				      and			 (x +zoom (i+1), y +zoom (j+1))			   r	 x	  r	y	  where	zoom  is the value of <STRONG>GL_ZOOM_X</STRONG>	and zoom  is the value	  of <STRONG>GL_ZOOM_Y</STRONG>.					y     <STRONG>EXAMPLES</STRONG>	  To copy the color pixel in the lower left corner of the	  window to the	current	raster position, use glCopyPixels(0,	  0, 1,	1, <STRONG>GL_COLOR</STRONG>);     <STRONG>NOTES</STRONG>	  Modes	specified by <STRONG>fglPixelStore</STRONG> have	no effect on the	  operation of <STRONG>fglCopyPixels</STRONG>.     <STRONG>ERRORS</STRONG>	  <STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>type</EM> is not an accepted	  value.	  <STRONG>GL_INVALID_VALUE</STRONG> is generated	if either <EM>width</EM>	or <EM>height</EM> is	  negative.	  <STRONG>GL_INVALID_OPERATION</STRONG> is generated if <EM>type</EM> is <STRONG>GL_DEPTH</STRONG>	and	  there	is no depth buffer.	  <STRONG>GL_INVALID_OPERATION</STRONG> is generated if <EM>type</EM> is <STRONG>GL_STENCIL</STRONG> and	  there	is no stencil buffer.	  <STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>fglCopyPixels</STRONG> is	  executed between the execution of <STRONG>fglBegin</STRONG> and the	  corresponding	execution of <STRONG>fglEnd</STRONG>.     <STRONG>ASSOCIATED</STRONG>	<STRONG>GETS</STRONG>	  <STRONG>fglGet</STRONG> with argument <STRONG>GL_CURRENT_RASTER_POSITION</STRONG>	  <STRONG>fglGet</STRONG> with argument <STRONG>GL_CURRENT_RASTER_POSITION_VALID</STRONG>     <STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>	  <STRONG>fglDepthFunc</STRONG>,	<STRONG>fglDrawBuffer</STRONG>, <STRONG>fglDrawPixels</STRONG>, <STRONG>fglPixelMap</STRONG>,	  <STRONG>fglPixelTransfer</STRONG>, <STRONG>fglPixelZoom</STRONG>, <STRONG>fglRasterPos</STRONG>,	<STRONG>fglReadBuffer</STRONG>,	  <STRONG>fglReadPixels</STRONG>, <STRONG>fglStencilFunc</STRONG></PRE></BODY></HTML>
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