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GLDRAWPIXELS(3G)		 OpenGL Manual		      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 * data);

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

       format
	   Specifies the format 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 data. 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.

       data
	   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() or glWindowPos() 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 data 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, or 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, or 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 × height pixels are read from memory, starting at location data.
       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.

       If a non-zero named buffer object is bound to the
       GL_PIXEL_UNPACK_BUFFER target (see glBindBuffer()) while a block of
       pixels is specified, data is treated as a byte offset into the buffer
       object's data store.

       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 format 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 format, 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 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 nth fragment such that x n = x r + n % widthy n
	   = y r + n width .sp where x r y 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 format, 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 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 nth index is written to location

	   x n = x r + n % widthy n = y r + n width

	   where x r y 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 format with
	   unspecified precision. Signed integer data is mapped linearly to
	   the internal floating-point format 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

	   x n = x r + n % widthy n = y r + n width

	   where x r y 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 format with unspecified precision. Signed integer
	   values are mapped linearly to the internal floating-point format
	   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 nth fragment such that

	   x n = x r + n % widthy n = y r + n width

	   where x r y 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 format 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 format 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 format 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 format 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 format 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 format 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 format 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 r y r 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 centers
       are in the rectangle with corners at

       x r + zoom x ⁢ n y r + zoom y ⁢ m.PP x r + zoom x ⁡ n + 1 y r + zoom y
       ⁡ m + 1

       where zoom x is the value of GL_ZOOM_X and zoom 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_ENUM is generated if format or type is not one of the
       accepted values.

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

       GL_INVALID_VALUE is generated if either width or height is negative.

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

       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_OPERATION is generated if format is one of
       GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV,
       GL_UNSIGNED_SHORT_5_6_5, or 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.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to the GL_PIXEL_UNPACK_BUFFER target and the buffer object's data
       store is currently mapped.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to the GL_PIXEL_UNPACK_BUFFER target and the data would be
       unpacked from the buffer object such that the memory reads required
       would exceed the data store size.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to the GL_PIXEL_UNPACK_BUFFER target and data is not evenly
       divisible into the number of bytes needed to store in memory a datum
       indicated by type.

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

ASSOCIATED GETS
       glGet() with argument GL_CURRENT_RASTER_POSITION

       glGet() with argument GL_CURRENT_RASTER_POSITION_VALID

       glGet() with argument GL_PIXEL_UNPACK_BUFFER_BINDING

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

COPYRIGHT
       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
       under the SGI Free Software B License. For details, see
       http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org			  04/29/2014		      GLDRAWPIXELS(3G)
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