fglDrawPixels(3G)
fglDrawPixels - write a block of pixels to the frame buffer
As shipped in IRIX 6.5.19. Last changed in IRIX 6.5.15.
NAME fglDrawPixels - write a block of pixels to the frame buffer FORTRAN SPECIFICATION SUBROUTINE fglDrawPixels( INTEGER*4 width, INTEGER*4 height, INTEGER*4 format, INTEGER*4 type, CHARACTER*8 pixels ) 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_ABGR_EXT, 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 fglDrawPixels 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 fglRasterPos to set the current raster position; use fglGet with argument GL_CURRENT_RASTER_POSITION_VALID to determine if the specified raster position is valid, and fglGet 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: fglPixelStore, fglPixelTransfer, fglPixelMap, and fglPixelZoom. This reference page describes the effects on fglDrawPixels 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 fglPixelStore). width x 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 fglPixelStore 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 fglPixelStore reference page for details on these options. The width x height pixels that are read from memory are each operated on in the same way, based on the values of several parameters specified by fglPixelTransfer and fglPixelMap. 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 b integer part of the index is then ANDed with 2 -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 = x + n mod width n r y = y + |n/width | n r where (x ,y ) is the current raster position. These pixel r r 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 b integer part of the index is then ANDed with 2 -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 = x + n mod width n r y = y + | n/width | n r where (x ,y ) is the current raster position. Only the pixel r r 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 = x + n mod width n r y = y + | n/width | n r where (x ,y ) is the current raster position. These pixel fragments r r 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 GL_ABGR_EXT 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; for GL_ABGR_EXT the order is alpha, blue, green, and then red. 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 = x + n mod width n r y = y + | n/width | n r where (x ,y ) is the current raster position. These pixel fragments r r 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 fglPixelZoom 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 r r 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 + zoom n, y + zoom m) r x r y (x + zoom (n + 1), y + zoom (m + 1)) r x r y where zoom is the value of GL_ZOOM_X and zoom is the value of x y GL_ZOOM_Y. When GL_INTERLACE_SGIX is enabled, every other row of the destination pixel rectangle is modified. The height of the pixel rectangle is equivalent to 2xGL_ZOOM_Yxheight. Only rows (y +0,y +2,...) are affected r r by the draw operation. Normally fglDrawPixels is synchronous: OpenGL executes a fglDrawPixels command in the order it is issued in the OpenGL command stream. Calling fglEnable with parameter GL_ASYNC_DRAW_PIXELS_SGIX causes subsequent fglDrawPixels commands to be asynchronous as defined by the SGIX_async extension. An asynchronous fglDrawPixels command samples the OpenGL state vector at the point in the OpenGL command stream where the command is issued, but the results of the command (e.g. updates to the frame buffer) do not happen until some unspecified time in the future. In particular, the order of the asynchronous command relative to other OpenGL commands issued later in the command stream is undefined. An implementation may choose to execute asynchronous commands in parallel with the normal command stream or at some convenient time in the future. Calling fglDisable with parameter GL_ASYNC_DRAW_PIXELS_SGIX restores the default synchronous behavior for subsequent fglDrawPixels commands. It does not affect any pending asynchronous fglDrawPixels commands, or wait for their completion. When an asynchronous fglDrawPixels command is issued, it is associated with the current value of GL_ASYNC_MARKER_SGIX as defined by the SGIX_async extension. A program can determine if an asynchronous fglDrawPixels command has completed by using the fglFinishAsyncSGIX or fglPollAsyncSGIX commands. There is a maximum number of asynchronous fglDrawPixels commands that can be outstanding at any one time, defined by the implementation. This value can be queried with fglGetIntegerv with argument GL_MAX_ASYNC_DRAW_PIXELS_SGIX. NOTES GL_BGR and GL_BGRA are only valid for format if the GL version is 1.2 or greater. GL_ABGR_EXT is valid only if the EXT_abgr extension is supported. 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_ABGR_EXT, 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 fglDrawPixels is executed between the execution of fglBegin and the corresponding execution of fglEnd. 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 not GL_RGBA, GL_BGRA or GL_ABGR_EXT. GL_INVALID_OPERATION is generated when the SGIX_subsample extension is supported, and the pixel storage mode GL_UNPACK_SUBSAMPLE_RATE_SGIX is not GL_PIXEL_SUBSAMPLE_4444_SGIX, and width is not a multiple of 2, or format is not a 3 or 4 component format, or type is a packed pixels type. GL_INVALID_OPERATION is generated if GL_ASYNC_DRAW_PIXELS_SGIX is enabled and the number of asynchronous fglDrawPixels commands that have been issued but not queried (using fglFinishAsyncSGIX or fglPollAsyncSGIX) exceeds GL_MAX_ASYNC_DRAW_PIXELS_SGIX. ASSOCIATED GETS fglGet with argument GL_CURRENT_RASTER_POSITION fglGet with argument GL_CURRENT_RASTER_POSITION_VALID fglGet with argument GL_INTERLACE_SGIX MACHINE DEPENDENCIES The SGIX_async and SGIX_async_pixel extensions are implemented only on Octane2 VPro systems. On RealityEngine, RealityEngine2, and VTX systems convolution may not be used in the following circumstances: 1. When rendering to pixmaps. 2. When fragment processing (texturing, depth buffering, alpha testing, multisampling, fog) is enabled. 3. When histogramming or minmax is enabled. 4. When either of the pixel zoom factors has a value other than 1.0 or -1.0. In these cases, fglDrawPixels and fglCopyPixels report a GL_INVALID_OPERATION error and do not transfer any pixels. Performance note for RealityEngine, RealityEngine2, and VTX systems: Unsigned color types use the fastest pixel-drawing path. Smaller types (e.g., GL_UNSIGNED_BYTE) require less host-to-graphics bandwidth, and are therefore faster than larger types (e.g., GL_UNSIGNED_INT). Signed and float types use the significantly slower floating-point pixel-drawing path. The slower pixel-drawing path is also used when the format is GL_DEPTH_COMPONENT and when fragment operations (i.e., depth or alpha testing, texturing, fog, etc.) are enabled. For best performance on XS, XZ, Elan, and Extreme systems set type to GL_UNSIGNED_BYTE and, when drawing to the color buffer, set format to GL_ABGR_EXT. On InfiniteReality systems, signed color-index pixels written to drawables with dual-personality (luminance + color-index) visuals will be sign-extended into the high-order bits of the framebuffer. For example, writing a signed byte value of 0x88 would yield 0xF88 in a 12-bit drawable. The SGIX_ycrcb extension is supported only on O2 systems. When using GL_YCRCB_422_SGIX with fglDrawPixels on O2 systems, an odd integer value for GL_UNPACK_SKIP_PIXELS will be set to the next highest even integer value to preserve color alignment. On CRIME systems with a Crime Revision of 1.0-1.3, the SGIX_ycrcb extension will generate incorrect RGB colors from video with highly saturated blue or red values. Commonly, the blue of a very saturated sky will be converted to a pale yellow. This problem is fixed with the CRIME 1.4 graphics. On Octane2 VPro systems the format GL_DEPTH_COMPONENT24_SGIX can be used to transfer depth pixel values to and from the depth buffer in their internal eye-space range. There are performance advantages over transfers that convert to screen-space values, particularly for GL_UNSIGNED_INT type pixels. The SGIX_interlace extension is supported only on InfiniteReality systems, on RealityEngine, RealityEngine2, and VTX systems, on Octane2 VPro systems, and on O2 systems. The EXT_packed_pixels extension is not supported on RealityEngine, RealityEngine2, and VTX systems. The SGIX_subsample and SGIX_resample extensions are supported only on Octane2 VPro systems. Applying the GL_PIXEL_SUBSAMPLE_2424_SGIX subsample rate is accelerated for direct immmediate mode transfers when the format is GL_RGB or GL_RGBA, and the type is GL_UNSIGNED_BYTE or GL_UNSIGNED_SHORT. SEE ALSO fglAlphaFunc, fglBlendFunc, fglCopyPixels, fglDepthFunc, fglLogicOp, fglPixelMap, fglPixelStore, fglPixelTransfer, fglPixelZoom, fglRasterPos, fglReadPixels, fglScissor, fglStencilFunc, fglAsyncMarkerSGIX, fglDeleteAsyncMarkersSGIX, fglFinishAsyncSGIX, fglGenAsyncMarkersSGIX, fglIsAsyncMarkerSGIX, fglPollAsyncSGIX