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GLDRAWPIXELS(3G)					      GLDRAWPIXELS(3G)

NAME
       glDrawPixels - write a block of pixels to the frame buffer

C SPECIFICATION
       void glDrawPixels( GLsizei width,
			  GLsizei height,
			  GLenum format,
			  GLenum type,
			  const GLvoid *pixels )

PARAMETERS
       width, height Specify the dimensions of the pixel rectangle to be writ‐
		     ten into the frame buffer.

       format	     Specifies the  of the  pixel  data.   Symbolic  constants
		     GL_COLOR_INDEX,   GL_STENCIL_INDEX,   GL_DEPTH_COMPONENT,
		     GL_RGB,  GL_BGR,  GL_RGBA,	 GL_BGRA,  GL_RED,   GL_GREEN,
		     GL_BLUE,  GL_ALPHA,  GL_LUMINANCE, and GL_LUMINANCE_ALPHA
		     are accepted.

       type	     Specifies the data type for pixels.   Symbolic  constants
		     GL_UNSIGNED_BYTE,	GL_BYTE, GL_BITMAP, GL_UNSIGNED_SHORT,
		     GL_SHORT,	   GL_UNSIGNED_INT,	GL_INT,	     GL_FLOAT,
		     GL_UNSIGNED_BYTE_3_3_2,	   GL_UNSIGNED_BYTE_2_3_3_REV,
		     GL_UNSIGNED_SHORT_5_6_5,	  GL_UNSIGNED_SHORT_5_6_5_REV,
		     GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
		     GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
		     GL_UNSIGNED_INT_8_8_8_8,	  GL_UNSIGNED_INT_8_8_8_8_REV,
		     GL_UNSIGNED_INT_10_10_10_2,			   and
		     GL_UNSIGNED_INT_2_10_10_10_REV are accepted.

       pixels	     Specifies a pointer to the pixel data.

DESCRIPTION
       glDrawPixels  reads pixel data from memory and writes it into the frame
       buffer
       relative to the current raster position, provided that the raster posi‐
       tion is valid.  Use
       glRasterPos to set the current raster position; use glGet with argument
       GL_CURRENT_RASTER_POSITION_VALID to determine if the  specified	raster
       position	 is  valid, and glGet with argument GL_CURRENT_RASTER_POSITION
       to query the raster position.

       Several parameters define the encoding of pixel data in memory and con‐
       trol  the processing of the pixel data before it is placed in the frame
       buffer.	These parameters are set  with	four  commands:	 glPixelStore,
       glPixelTransfer,	 glPixelMap,  and  glPixelZoom.	  This	reference page
       describes the effects on glDrawPixels of many,  but  not	 all,  of  the
       parameters specified by these four commands.

       Data  is	 read  from  pixels as a sequence of signed or unsigned bytes,
       signed or unsigned shorts, signed or unsigned integers, or  single-pre‐
       cision  floating-point  values, depending on type.  When type is one of
       GL_UNSIGNED_BYTE,      GL_BYTE,	    GL_UNSIGNED_SHORT,	     GL_SHORT,
       GL_UNSIGNED_INT, GL_INT, or GL_FLOAT each of these bytes, shorts, inte‐
       gers, or floating-point values is interpreted as	 one  color  or	 depth
       component,  or  one  index,  depending  on format.  When type is one of
       GL_UNSIGNED_BYTE_3_3_2,			      GL_UNSIGNED_SHORT_5_6_5,
       GL_UNSIGNED_SHORT_4_4_4_4,		    GL_UNSIGNED_SHORT_5_5_5_1,
       GL_UNSIGNED_INT_8_8_8_8,	 GL_UNSIGNED_INT_10_10_10_2,   each   unsigned
       value  is  interpreted  as  containing  all the components for a single
       pixel, with the color components arranged according  to	format.	  When
       type is one of GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5_REV,
       GL_UNSIGNED_SHORT_4_4_4_4_REV,		GL_UNSIGNED_SHORT_1_5_5_5_REV,
       GL_UNSIGNED_INT_8_8_8_8_REV,    GL_UNSIGNED_INT_2_10_10_10_REV,	  each
       unsigned value is interpreted as containing all color components, spec‐
       ified  by  format,  for a single pixel in a reversed order. Indices are
       always treated individually.  Color components are treated as groups of
       one, two, three, or four values, again based on format. Both individual
       indices and groups of components are referred to as pixels.  If type is
       GL_BITMAP,  the	data must be unsigned bytes, and format must be either
       GL_COLOR_INDEX or GL_STENCIL_INDEX.  Each unsigned byte is  treated  as
       eight 1-bit pixels, with bit ordering determined by GL_UNPACK_LSB_FIRST
       (see glPixelStore).

       width×height pixels are read from memory, starting at location  pixels.
       By  default,  these  pixels  are	 taken from adjacent memory locations,
       except that after all width  pixels  are	 read,	the  read  pointer  is
       advanced	 to  the next four-byte boundary.  The four-byte row alignment
       is specified by glPixelStore with argument GL_UNPACK_ALIGNMENT, and  it
       can be set to one, two, four, or eight bytes.  Other pixel store param‐
       eters specify different read  pointer  advancements,  both  before  the
       first  pixel  is	 read  and  after  all width pixels are read.  See the
       glPixelStore reference page for details on these options.

       The width×height pixels that are read from memory are each operated  on
       in the same way, based on the values of several parameters specified by
       glPixelTransfer and glPixelMap.	The details of	these  operations,  as
       well as the target buffer into which the pixels are drawn, are specific
       to the  of the pixels, as specified by format.  format can  assume  one
       of 13 symbolic values:

       GL_COLOR_INDEX
		 Each pixel is a single value, a color index.  It is converted
		 to fixed-point , with an unspecified number of	 bits  to  the
		 right	of  the	 binary	 point,	 regardless of the memory data
		 type.	Floating-point values convert to true fixed-point val‐
		 ues.	Signed and unsigned integer data is converted with all
		 fraction bits set to 0.  Bitmap data convert to either	 0  or
		 1.

		 Each fixed-point index is then shifted left by GL_INDEX_SHIFT
		 bits and added to GL_INDEX_OFFSET.  If GL_INDEX_SHIFT is neg‐
		 ative,	 the shift is to the right.  In either case, zero bits
		 fill otherwise unspecified bit locations in the result.

		 If the GL is in RGBA mode, the resulting index	 is  converted
		 to  an	 RGBA  pixel with the help of the GL_PIXEL_MAP_I_TO_R,
		 GL_PIXEL_MAP_I_TO_G,	      GL_PIXEL_MAP_I_TO_B,	   and
		 GL_PIXEL_MAP_I_TO_A  tables.	If  the	 GL  is in color index
		 mode, and if GL_MAP_COLOR is true, the index is replaced with
		 the	value	 that	 it   references   in	lookup	 table
		 GL_PIXEL_MAP_I_TO_I.  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.

		 The  GL then converts the resulting indices or RGBA colors to
		 fragments by attaching the current raster position z  coordi‐
		 nate  and texture coordinates to each pixel, then assigning x
		 and y window coordinates to the nth fragment such that

					xn=xr+nmodwidth

					yn=yr+⌊n/width⌋

		 where (xr,yr) is the current raster  position.	  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.

       GL_STENCIL_INDEX
		 Each pixel is a single value, a stencil index.	  It  is  con‐
		 verted to fixed-point , with an unspecified number of bits to
		 the right of the binary point, regardless of the memory  data
		 type.	Floating-point values convert to true fixed-point val‐
		 ues.  Signed and unsigned integer data is converted with  all
		 fraction  bits	 set to 0.  Bitmap data convert to either 0 or
		 1.

		 Each fixed-point index is then shifted left by GL_INDEX_SHIFT
		 bits,	and  added  to	GL_INDEX_OFFSET.  If GL_INDEX_SHIFT is
		 negative, the shift is to the right.  In  either  case,  zero
		 bits  fill otherwise unspecified bit locations in the result.
		 If GL_MAP_STENCIL is true, the index  is  replaced  with  the
		 value that it references in lookup table GL_PIXEL_MAP_S_TO_S.
		 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 nth index is written to location

				      xn=xr+nmodwidth

				      yn=yr+⌊n/width⌋

	      where (xr,yr) is the current raster position.   Only  the	 pixel
	      ownership	 test,	the  scissor  test,  and the stencil writemask
	      affect these write operations.

       GL_DEPTH_COMPONENT
	      Each pixel is a single-depth component.  Floating-point data  is
	      converted directly to an internal floating-point
	       with unspecified precision.  Signed integer data is mapped lin‐
	      early to the internal floating-point
	       such that the most positive representable integer value maps to
	      1.0,  and	 the  most  negative representable value maps to -1.0.
	      Unsigned integer data is mapped similarly: the  largest  integer
	      value  maps  to 1.0, and 0 maps to 0.0.  The resulting floating-
	      point depth value is then multiplied by GL_DEPTH_SCALE and added
	      to GL_DEPTH_BIAS.	 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 x and y
	      window coordinates to the nth fragment such that

				      xn=xr+nmodwidth

				      yn=yr+⌊n/width⌋

	      where (xr,yr) is the current raster position.  These pixel frag‐
	      ments are then treated just like the fragments generated by ras‐
	      terizing points, lines, or polygons.  Texture mapping, fog,  and
	      all the fragment operations are applied before the fragments are
	      written to the frame buffer.

       GL_RGBA

       GL_BGRA
	      Each pixel is a four-component group: for GL_RGBA, the red  com‐
	      ponent  is  first, followed by green, followed by blue, followed
	      by alpha; for GL_BGRA the order is blue,	green,	red  and  then
	      alpha.   Floating-point  values  are  converted  directly	 to an
	      internal floating-point
	       with unspecified precision.  Signed integer values  are	mapped
	      linearly to the internal floating-point
	       such that the most positive representable integer value maps to
	      1.0, and the most negative representable	value  maps  to	 -1.0.
	      (Note  that  this	 mapping does not convert 0 precisely to 0.0.)
	      Unsigned integer data is mapped similarly: the  largest  integer
	      value  maps  to 1.0, and 0 maps to 0.0.  The resulting floating-
	      point color values are then multiplied by GL_c_SCALE  and	 added
	      to  GL_c_BIAS,  where  c	is RED, GREEN, BLUE, and ALPHA for the
	      respective color components.  The results	 are  clamped  to  the
	      range [0,1].

	      If  GL_MAP_COLOR	is true, each color component is scaled by the
	      size of lookup table GL_PIXEL_MAP_c_TO_c, then replaced  by  the
	      value  that  it  references  in  that table.  c is R, G, B, or A
	      respectively.

	      The GL then converts the resulting RGBA colors to	 fragments  by
	      attaching	 the  current raster position z coordinate and texture
	      coordinates to each pixel, then assigning x and y window coordi‐
	      nates to the nth fragment such that

				      xn=xr+nmodwidth

				      yn=yr+⌊n/width⌋

	      where (xr,yr) is the current raster position.  These pixel frag‐
	      ments are then treated just like the fragments generated by ras‐
	      terizing	points, lines, or polygons.  Texture mapping, fog, and
	      all the fragment operations are applied before the fragments are
	      written to the frame buffer.

       GL_RED Each  pixel  is  a single red component.	This component is con‐
	      verted to the internal floating-point  in the same way  the  red
	      component	 of  an RGBA pixel is. It is then converted to an RGBA
	      pixel with green and blue set to 0, and alpha set to  1.	 After
	      this  conversion, the pixel is treated as if it had been read as
	      an RGBA pixel.

       GL_GREEN
	      Each pixel is a single green component.  This component is  con‐
	      verted to the internal floating-point  in the same way the green
	      component of an RGBA pixel is.  It is then converted to an  RGBA
	      pixel  with  red	and  blue set to 0, and alpha set to 1.	 After
	      this conversion, the pixel is treated as if it had been read  as
	      an RGBA pixel.

       GL_BLUE
	      Each  pixel  is a single blue component.	This component is con‐
	      verted to the internal floating-point  in the same way the  blue
	      component	 of an RGBA pixel is.  It is then converted to an RGBA
	      pixel with red and green set to 0, and alpha set	to  1.	 After
	      this  conversion, the pixel is treated as if it had been read as
	      an RGBA pixel.

       GL_ALPHA
	      Each pixel is a single alpha component.  This component is  con‐
	      verted to the internal floating-point  in the same way the alpha
	      component of an RGBA pixel is.  It is then converted to an  RGBA
	      pixel  with  red,	 green, and blue set to 0.  After this conver‐
	      sion, the pixel is treated as if it had been  read  as  an  RGBA
	      pixel.

       GL_RGB

       GL_BGR Each  pixel  is  a three-component group: red first, followed by
	      green, followed by blue; for  GL_BGR,  the  first	 component  is
	      blue,  followed  by  green and then red.	Each component is con‐
	      verted to the internal floating-point  in the same way the  red,
	      green,  and  blue	 components  of	 an RGBA pixel are.  The color
	      triple is converted to an RGBA pixel with alpha set to 1.	 After
	      this  conversion, the pixel is treated as if it had been read as
	      an RGBA pixel.

       GL_LUMINANCE
	      Each pixel is a single luminance component.  This	 component  is
	      converted	 to  the  internal floating-point  in the same way the
	      red component of an RGBA pixel is.  It is then converted	to  an
	      RGBA  pixel with red, green, and blue set to the converted lumi‐
	      nance value, and alpha set to 1.	 After	this  conversion,  the
	      pixel is treated as if it had been read as an RGBA pixel.

       GL_LUMINANCE_ALPHA
	      Each  pixel  is a two-component group: luminance first, followed
	      by alpha.	 The two components  are  converted  to	 the  internal
	      floating-point   in  the	same  way the red component of an RGBA
	      pixel is.	 They are then converted to an RGBA  pixel  with  red,
	      green,  and blue set to the converted luminance value, and alpha
	      set to the converted alpha value.	 After	this  conversion,  the
	      pixel is treated as if it had been read as an RGBA pixel.

       The  following  table summarizes the meaning of the valid constants for
       the type parameter:

──────────────────────────────────────────────────────────────────────────────────────────
Type				 Corresponding Type
──────────────────────────────────────────────────────────────────────────────────────────
GL_UNSIGNED_BYTE		 unsigned 8-bit integer
GL_BYTE				 signed 8-bit integer
GL_BITMAP			 single bits in unsigned 8-bit integers
GL_UNSIGNED_SHORT		 unsigned 16-bit integer
GL_SHORT			 signed 16-bit integer
GL_UNSIGNED_INT			 unsigned 32-bit integer
GL_INT				 32-bit integer
GL_FLOAT			 single-precision floating-point
GL_UNSIGNED_BYTE_3_3_2		 unsigned 8-bit integer
GL_UNSIGNED_BYTE_2_3_3_REV	 unsigned 8-bit integer with reversed component ordering
GL_UNSIGNED_SHORT_5_6_5		 unsigned 16-bit integer
GL_UNSIGNED_SHORT_5_6_5_REV	 unsigned 16-bit integer with reversed component ordering
GL_UNSIGNED_SHORT_4_4_4_4	 unsigned 16-bit integer
GL_UNSIGNED_SHORT_4_4_4_4_REV	 unsigned 16-bit integer with reversed component ordering
GL_UNSIGNED_SHORT_5_5_5_1	 unsigned 16-bit integer
GL_UNSIGNED_SHORT_1_5_5_5_REV	 unsigned 16-bit integer with reversed component ordering
GL_UNSIGNED_INT_8_8_8_8		 unsigned 32-bit integer
GL_UNSIGNED_INT_8_8_8_8_REV	 unsigned 32-bit integer with reversed component ordering
GL_UNSIGNED_INT_10_10_10_2	 unsigned 32-bit integer
GL_UNSIGNED_INT_2_10_10_10_REV	 unsigned 32-bit integer with reversed component ordering
──────────────────────────────────────────────────────────────────────────────────────────

       The rasterization described so far assumes pixel zoom factors of 1.  If
       glPixelZoom is used to change the x and y pixel	zoom  factors,	pixels
       are  converted  to  fragments  as  follows.  If (xr, yr) is the current
       raster position, and a given pixel is in the nth column and mth row  of
       the pixel rectangle, then fragments are generated for pixels whose cen‐
       ters are in the rectangle with corners at

				   (xr+zoomxn, yr+zoomym)

			       (xr+zoomx(n+1), yr+zoomy(m+1))

       where zoomx is the value	 of  GL_ZOOM_X	and  zoomy  is	the  value  of
       GL_ZOOM_Y.

NOTES
       GL_BGR  and  GL_BGRA are only valid for format if the GL version is 1.2
       or greater.

       GL_UNSIGNED_BYTE_3_3_2,			   GL_UNSIGNED_BYTE_2_3_3_REV,
       GL_UNSIGNED_SHORT_5_6_5,			  GL_UNSIGNED_SHORT_5_6_5_REV,
       GL_UNSIGNED_SHORT_4_4_4_4,		GL_UNSIGNED_SHORT_4_4_4_4_REV,
       GL_UNSIGNED_SHORT_5_5_5_1,		GL_UNSIGNED_SHORT_1_5_5_5_REV,
       GL_UNSIGNED_INT_8_8_8_8,			  GL_UNSIGNED_INT_8_8_8_8_REV,
       GL_UNSIGNED_INT_10_10_10_2, and GL_UNSIGNED_INT_2_10_10_10_REV are only
       valid for type if the GL version is 1.2 or greater.

ERRORS
       GL_INVALID_VALUE is generated if either width or height is negative.

       GL_INVALID_ENUM is generated if format  or  type	 is  not  one  of  the
       accepted values.

       GL_INVALID_OPERATION  is	 generated  if	format	is  GL_RED,  GL_GREEN,
       GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA, GL_BGR, GL_BGRA,  GL_LUMINANCE,  or
       GL_LUMINANCE_ALPHA, and the GL is in color index mode.

       GL_INVALID_ENUM	is  generated  if  type is GL_BITMAP and format is not
       either GL_COLOR_INDEX or GL_STENCIL_INDEX.

       GL_INVALID_OPERATION is generated if  format  is	 GL_STENCIL_INDEX  and
       there is no stencil buffer.

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

       GL_INVALID_OPERATION    is    generated	  if	 format	    is	   one
       GL_UNSIGNED_BYTE_3_3_2,			   GL_UNSIGNED_BYTE_2_3_3_REV,
       GL_UNSIGNED_SHORT_5_6_5, of GL_UNSIGNED_SHORT_5_6_5_REV and  format  is
       not GL_RGB.

       GL_INVALID_OPERATION    is    generated	  if	format	 is   one   of
       GL_UNSIGNED_SHORT_4_4_4_4,		GL_UNSIGNED_SHORT_4_4_4_4_REV,
       GL_UNSIGNED_SHORT_5_5_5_1,		GL_UNSIGNED_SHORT_1_5_5_5_REV,
       GL_UNSIGNED_INT_8_8_8_8,			  GL_UNSIGNED_INT_8_8_8_8_REV,
       GL_UNSIGNED_INT_10_10_10_2,  or GL_UNSIGNED_INT_2_10_10_10_REV and for‐
       mat is neither GL_RGBA nor GL_BGRA.

ASSOCIATED GETS
       glGet with argument GL_CURRENT_RASTER_POSITION
       glGet with argument GL_CURRENT_RASTER_POSITION_VALID

SEE ALSO
       glAlphaFunc(3G),	 glBlendFunc(3G),  glCopyPixels(3G),  glDepthFunc(3G),
       glLogicOp(3G),  glPixelMap(3G),	glPixelStore(3G), glPixelTransfer(3G),
       glPixelZoom(3G),	 glRasterPos(3G),   glReadPixels(3G),	glScissor(3G),
       glStencilFunc(3G)

							      GLDRAWPIXELS(3G)
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