glDrawPixels — write a block of pixels to the frame buffer
void glDrawPixels( | GLsizei | width, |
GLsizei | height, | |
GLenum | format, | |
GLenum | type, | |
const GLvoid * | data) ; |
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.
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).
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
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
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
where
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
where
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
GL_DEPTH_SCALE
and added to GL_DEPTH_BIAS
.
The result is clamped to the range
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
where
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
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
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
where
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
where
GL_ZOOM_X
and
GL_ZOOM_Y
.
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.
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.
glGet with argument GL_CURRENT_RASTER_POSITION
glGet with argument GL_CURRENT_RASTER_POSITION_VALID
glGet with argument GL_PIXEL_UNPACK_BUFFER_BINDING
glAlphaFunc, glBlendFunc, glCopyPixels, glDepthFunc, glLogicOp, glPixelMap, glPixelStore, glPixelTransfer, glPixelZoom, glRasterPos, glReadPixels, glScissor, glStencilFunc, glWindowPos
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/.