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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 )

       delim $$

PARAMETERS
       width, height
	      Specify the dimensions of the pixel rectangle to be written 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
       position 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
       control 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-precision 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,
       integers, 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,
       specified 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$~ times ~$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 parameters 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$~ times ~$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
		 values.  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 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 $2 sup b -1$, 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
		 coordinate and texture coordinates to each pixel, then
		 assigning $x$ and $y$ window coordinates to the $n$th
		 fragment such that

		 $x sub n ~=~ x sub r ~+~ n ~ roman mod ~ "width"$

		 $y sub n ~=~ y sub r ~+~ |_ n ^/^ "width" ~ _|$

	      where ($x sub r , y sub r$) 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 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 values.
	      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 $2 sup b -1$, 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
	      $n$th index is written to location
	      $x sub n ~=~ x sub r ~+~ n ~ roman mod ~ "width"$

	      $y sub n ~=~ y sub r ~+~ |_ ~ n / "width" ~ _|$

	      where ($x sub r , y sub r$) 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
	      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.  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 $n$th fragment such that
	      $x sub n ~=~ x sub r ~+~ n ~ roman mod ~ "width"$

	      $y sub n ~=~ y sub r ~+~ |_ ~ n / "width" ~ _|$

	      where ($x sub r , y sub r$) 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_RGBA

       GL_BGRA
	      Each pixel is a four-component group: for GL_RGBA, the red
	      component 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
	      coordinates to the $n$th fragment such that
	      $x sub n ~=~ x sub r ~+~ n ~ roman mod ~ "width"$

	      $y sub n ~=~ y sub r ~+~ |_ ~ n / "width" ~ _|$

	      where ($x sub r , y sub r$) 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_RED Each pixel is a single red 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 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
	      converted 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
	      converted 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
	      converted 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
	      conversion, 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
	      converted 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
	      luminance 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 ($x sub r$, $y sub
       r$) is the current raster position, and a given pixel is in the $n$th
       column and $m$th row of the pixel rectangle, then fragments are
       generated for pixels whose centers are in the rectangle with corners at

	      ($x sub r ~+~ zoom sub x^ n$, $y sub r ~+~ zoom sub y^ m$)

	      ($x sub r ~+~ zoom sub x^ (n ~+~ 1)$, $y sub r ~+~ zoom sub y^ (
	      m ~+~ 1 )$)

       where $zoom sub x$ is the value of GL_ZOOM_X and $zoom sub y$ 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
       format 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)

								 March 1, 2011
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