fglPixelStore(3G)
fglPixelStoref, fglPixelStorei - set pixel storage modes
As shipped in IRIX 6.5.22. Last changed in IRIX 6.5.15.
NAME fglPixelStoref, fglPixelStorei - set pixel storage modes FORTRAN SPECIFICATION SUBROUTINE fglPixelStoref( INTEGER*4 pname, REAL*4 param ) SUBROUTINE fglPixelStorei( INTEGER*4 pname, INTEGER*4 param ) PARAMETERS pname Specifies the symbolic name of the parameter to be set. Twelve values affect the packing of pixel data into memory: GL_PACK_SWAP_BYTES, GL_PACK_LSB_FIRST, GL_PACK_ROW_LENGTH, GL_PACK_IMAGE_HEIGHT, GL_PACK_IMAGE_DEPTH_SGIS, GL_PACK_SKIP_PIXELS, GL_PACK_SKIP_ROWS, GL_PACK_SKIP_IMAGES, GL_PACK_SKIP_VOLUMES_SGIS, GL_PACK_ALIGNMENT, GL_PACK_SUBSAMPLE_RATE_SGIX, and GL_PACK_RESAMPLE_SGIX. Twelve more affect the unpacking of pixel data from memory: GL_UNPACK_SWAP_BYTES, GL_UNPACK_LSB_FIRST, GL_UNPACK_ROW_LENGTH, GL_UNPACK_IMAGE_HEIGHT, GL_UNPACK_IMAGE_DEPTH_SGIS, GL_UNPACK_SKIP_PIXELS, GL_UNPACK_SKIP_ROWS, GL_UNPACK_SKIP_IMAGES, GL_UNPACK_SKIP_VOLUMES_SGIS, GL_UNPACK_ALIGNMENT, GL_UNPACK_SUBSAMPLE_RATE_SGIX, and GL_UNPACK_RESAMPLE_SGIX. param Specifies the value that pname is set to. DESCRIPTION fglPixelStore sets pixel storage modes that affect the operation of subsequent fglDrawPixels and fglReadPixels as well as the unpacking of polygon stipple patterns (see fglPolygonStipple), bitmaps (see fglBitmap), and texture patterns (see fglTexImage1D, fglTexImage2D, fglTexImage3D, fglTexImage4DSGIS, fglTexSubImage1D, fglTexSubImage2D, fglTexSubImage3D, and fglTexSubImage4DSGIS). Additionally, if the GL_ARB_imaging extension is supported, pixel storage modes affect convolution filters (see fglConvolutionFilter1D, fglConvolutionFilter2D, and fglSeparableFilter2D), color tables (see fglColorTable and fglColorSubTable), and unpacking histogram (see fglHistogram) and minmax (see fglMinmax) data. pname is a symbolic constant indicating the parameter to be set, and param is the new value. Twelve of the twenty-four storage parameters affect how pixel data is returned to client memory. They are as follows: GL_PACK_SWAP_BYTES If true, byte ordering for multibyte color components, depth components, color indices, or stencil indices is reversed. That is, if a four-byte component consists of bytes b , b , b , 0 1 2 b , it is stored in memory as b , b , b , b if 3 3 2 1 0 GL_PACK_SWAP_BYTES is true. GL_PACK_SWAP_BYTES has no effect on the memory order of components within a pixel, only on the order of bytes within components or indices. For example, the three components of a GL_RGB format pixel are always stored with red first, green second, and blue third, regardless of the value of GL_PACK_SWAP_BYTES. GL_PACK_LSB_FIRST If true, bits are ordered within a byte from least significant to most significant; otherwise, the first bit in each byte is the most significant one. This parameter is significant for bitmap data only. GL_PACK_ROW_LENGTH If greater than 0, GL_PACK_ROW_LENGTH defines the number of pixels in a row. If the first pixel of a row is placed at location p in memory, then the location of the first pixel of the next row is obtained by skipping ( |nl s > a k = | _|___| s < a | s| a | ( components or indices, where n is the number of components or indices in a pixel, l is the number of pixels in a row (GL_PACK_ROW_LENGTH if it is greater than 0, the width argument to the pixel routine otherwise), a is the value of GL_PACK_ALIGNMENT, and s is the size, in bytes, of a single component (if a<s, then it is as if a = s). In the case of 1- bit values, the location of the next row is obtained by skipping |__| k = 8a |8a| components or indices. The word component in this description refers to the nonindex values red, green, blue, alpha, and depth. Storage format GL_RGB, for example, has three components per pixel: first red, then green, and finally blue. GL_PACK_IMAGE_HEIGHT If greater than 0, GL_PACK_IMAGE_HEIGHT defines the number of pixels in an image of a three-dimensional texture volume, where an ``image'' consists of all pixels sharing the same third dimension index. If the first pixel of an image is placed at location p in memory, then the location of the first pixel of the next image is obtained by skipping ( | nlh s > a k = | _|____| s < a | s| a | ( components or indices, where n is the number of components or indices in a pixel, l is the number of pixels in a row (GL_PACK_ROW_LENGTH if it is greater than 0, the width argument to fglTexImage3D otherwise), h is the number of rows in a pixel image (GL_PACK_IMAGE_HEIGHT if it is greater than 0, the height argument to the fglTexImage3D routine otherwise), a is the value of GL_PACK_ALIGNMENT, and s is the size, in bytes, of a single component (if a<s, then it is as if a=s). The word component in this description refers to the nonindex values red, green, blue, alpha, and depth. Storage format GL_RGB, for example, has three components per pixel: first red, then green, and finally blue. GL_PACK_IMAGE_DEPTH_SGIS If greater than 0, GL_PACK_IMAGE_DEPTH_SGIS defines the number of pixels in a volume of a four-dimensional texture hypervolume, where a ``volume'' consists of all pixels sharing the same fourth dimension index. If the first pixel of a volume is placed at location p in memory, then the location of the first pixel of the next volume is obtained by skipping ( | nlhd s > a k = | _|_____| s < a | s| a | ( components or indices, where n is the number of components or indices in a pixel, l is the number of pixels in a row (GL_PACK_ROW_LENGTH if it is greater than 0, the width argument to fglTexImage4DSGIS otherwise, h is the number of rows in a pixel image (GL_PACK_IMAGE_HEIGHT if it is greater than 0, the height argument to the fglTexImage4DSGIS routine otherwise), d is the number of images in a volume (GL_PACK_IMAGE_DEPTH_SGIS if it is greater than 0, the depth argument to the fglTexImage4DSGIS routine otherwise), a is the value of GL_PACK_ALIGNMENT, and s is the size, in bytes, of a single component (if a<s, then it is as if a=s). The word component in this description refers to the nonindex values red, green, blue, alpha, and depth. Storage format GL_RGB, for example, has three components per pixel: first red, then green, and finally blue. GL_PACK_SKIP_PIXELS, GL_PACK_SKIP_ROWS, GL_PACK_SKIP_IMAGES, and GL_PACK_SKIP_VOLUMES_SGIS These values are provided as a convenience to the programmer; they provide no functionality that cannot be duplicated simply by incrementing the pointer passed to fglReadPixels. Setting GL_PACK_SKIP_PIXELS to i is equivalent to incrementing the pointer by in components or indices, where n is the number of components or indices in each pixel. Setting GL_PACK_SKIP_ROWS to j is equivalent to incrementing the pointer by jm components or indices, where m is the number of components or indices per row, as just computed in the GL_PACK_ROW_LENGTH section. Setting GL_PACK_SKIP_IMAGES to k is equivalent to incrementing the pointer by kp, where p is the number of components or indices per image, as computed in the GL_PACK_IMAGE_HEIGHT section. Setting GL_PACK_SKIP_VOLUMES_SGIS to k is equivalent to incrementing the pointer by kp, where p is the number of components or indices per volume, as computed in the GL_PACK_IMAGE_DEPTH_SGIS section. GL_PACK_ALIGNMENT Specifies the alignment requirements for the start of each pixel row in memory. The allowable values are 1 (byte- alignment), 2 (rows aligned to even-numbered bytes), 4 (word- alignment), and 8 (rows start on double-word boundaries). GL_PACK_SUBSAMPLE_RATE_SGIX Specifies the subsample conversion rate that is applied to packed pixel stores. The accepted param values are GL_PIXEL_SUBSAMPLE_4444_SGIX, GL_PIXEL_SUBSAMPLE_2424_SGIX, and GL_PIXEL_SUBSAMPLE_4242_SGIX. When set to other than the default GL_PIXEL_SUBSAMPLE_4444_SGIX value, RGB and RGBA pixel groups are sampled to produce two-value packed pixel groups. The width argument to the pixel routine must be a multiple of 2 pixels. The red, green, and blue components of the pixel are sampled in the order specified by the destination format. When a 4-component format is specified, the alpha component is ignored. Subsampled pixel pairs are packed as follows: 2424 - decimate : 4242 - decimate : <U00,U01,U02> <U10,U11,U12> <U00,U01,U02> <U10,U11,U12> | | | | | | |___ ___| | | | | \ / \ / | | \ / X X | | \ / / \ / \ | | | | | | | | V V V V V V V V <P00,P01> <P10,P11> <P00,P01> <P10,P11> GL_PACK_RESAMPLE_SGIX Specifies the resample mode in effect when a pack subsample rate is being applied. The only currently allowable value is GL_RESAMPLE_DECIMATE_SGIX. When the subsample rate is not uniform for all components, the components that are sampled at the lower-rate in the second group of each pixel pair are ignored. The other twelve of the twenty-four storage parameters affect how pixel data is read from client memory. These values are significant for fglDrawPixels, fglTexImage1D, fglTexImage2D, fglTexImage3D, fglTexImage4DSGIS, fglTexSubImage1D, fglTexSubImage2D, fglTexSubImage3D, fglTexSubImage4DSGIS, fglBitmap, and fglPolygonStipple. Additionally, if the GL_ARB_imaging extension is supported, fglColorTable, fglColorSubTable, fglConvolutionFilter1D, fglConvolutionFilter2D, and fglSeparableFilter2D. They are as follows: GL_UNPACK_SWAP_BYTES If true, byte ordering for multibyte color components, depth components, color indices, or stencil indices is reversed. That is, if a four-byte component consists of bytes b , b , b , b , it is 0 1 2 3 taken from memory as b , b , b , b if GL_UNPACK_SWAP_BYTES is true. 3 2 1 0 GL_UNPACK_SWAP_BYTES has no effect on the memory order of components within a pixel, only on the order of bytes within components or indices. For example, the three components of a GL_RGB format pixel are always stored with red first, green second, and blue third, regardless of the value of GL_UNPACK_SWAP_BYTES. GL_UNPACK_LSB_FIRST If true, bits are ordered within a byte from least significant to most significant; otherwise, the first bit in each byte is the most significant one. This is relevant only for bitmap data. GL_UNPACK_ROW_LENGTH If greater than 0, GL_UNPACK_ROW_LENGTH defines the number of pixels in a row. If the first pixel of a row is placed at location p in memory, then the location of the first pixel of the next row is obtained by skipping ( | nl s > a k = | _|___| s < a | s| a | ( components or indices, where n is the number of components or indices in a pixel, l is the number of pixels in a row (GL_UNPACK_ROW_LENGTH if it is greater than 0, the width argument to the pixel routine otherwise), a is the value of GL_UNPACK_ALIGNMENT, and s is the size, in bytes, of a single component (if a<s, then it is as if a=s). In the case of 1-bit values, the location of the next row is obtained by skipping |__| k = 8a |8a| components or indices. The word component in this description refers to the nonindex values red, green, blue, alpha, and depth. Storage format GL_RGB, for example, has three components per pixel: first red, then green, and finally blue. GL_UNPACK_IMAGE_HEIGHT If greater than 0, GL_UNPACK_IMAGE_HEIGHT defines the number of pixels in an image of a three-dimensional texture volume, where an ``image'' consists of all pixels sharing the same third dimension index. If the first pixel of an image is placed at location p in memory, then the location of the first pixel of the next image is obtained by skipping ( | nlh s > a k = | _|____| s < a | s| a | ( components or indices, where n is the number of components or indices in a pixel, l is the number of pixels in a row (GL_UNPACK_ROW_LENGTH if it is greater than 0, the width argument to fglTexImage3D otherwise), h is the number of rows in an image (GL_UNPACK_IMAGE_HEIGHT if it is greater than 0, the height argument to fglTexImage3D otherwise), a is the value of GL_UNPACK_ALIGNMENT, and s is the size, in bytes, of a single component (if a<s, then it is as if a = s). The word component in this description refers to the nonindex values red, green, blue, alpha, and depth. Storage format GL_RGB, for example, has three components per pixel: first red, then green, and finally blue. GL_UNPACK_IMAGE_DEPTH_SGIS If greater than 0, GL_UNPACK_IMAGE_DEPTH_SGIS defines the number of pixels in a volume of a four-dimensional texture hypervolume, where a ``volume'' consists of all pixels sharing the same fourth dimension index. If the first pixel of a volume is placed at location p in memory, then the location of the first pixel of the next volume is obtained by skipping ( | nlhd s > a k = | _|_____| s < a | s| a | ( components or indices, where n is the number of components or indices in a pixel, l is the number of pixels in a row (GL_UNPACK_ROW_LENGTH if it is greater than 0, the width argument to fglTexImage3D otherwise), h is the number of rows in an image (GL_UNPACK_IMAGE_HEIGHT if it is greater than 0, the height argument to fglTexImage3D otherwise), d is the number of images in a volume (GL_UNPACK_IMAGE_DEPTH_SGIS if it is greater than 0, the depth argument to the fglTexImage4DSGIS routine otherwise), a is the value of GL_UNPACK_ALIGNMENT, and s is the size, in bytes, of a single component (if a<s, then it is as if a = s). The word component in this description refers to the nonindex values red, green, blue, alpha, and depth. Storage format GL_RGB, for example, has three components per pixel: first red, then green, and finally blue. GL_UNPACK_SKIP_PIXELS, GL_UNPACK_SKIP_ROWS, GL_UNPACK_SKIP_IMAGES, and GL_UNPACK_SKIP_VOLUMES_SGIS These values are provided as a convenience to the programmer; they provide no functionality that cannot be duplicated by incrementing the pointer passed to fglDrawPixels, fglTexImage1D, fglTexImage2D, fglTexSubImage1D, fglTexSubImage2D, fglBitmap, or fglPolygonStipple. Setting GL_UNPACK_SKIP_PIXELS to i is equivalent to incrementing the pointer by in components or indices, where n is the number of components or indices in each pixel. Setting GL_UNPACK_SKIP_ROWS to j is equivalent to incrementing the pointer by jk components or indices, where k is the number of components or indices per row, as just computed in the GL_UNPACK_ROW_LENGTH section. Setting GL_UNPACK_SKIP_IMAGES to k is equivalent to incrementing the pointer by kp, where p is the number of components or indices per image, as computed in the GL_UNPACK_IMAGE_HEIGHT section. Setting GL_UNPACK_SKIP_VOLUMES_SGIS to k is equivalent to incrementing the pointer by kp, where p is the number of components or indices per volume, as computed in the GL_UNPACK_IMAGE_DEPTH_SGIS section. GL_UNPACK_ALIGNMENT Specifies the alignment requirements for the start of each pixel row in memory. The allowable values are 1 (byte-alignment), 2 (rows aligned to even-numbered bytes), 4 (word-alignment), and 8 (rows start on double-word boundaries). GL_UNPACK_SUBSAMPLE_RATE_SGIX Specifies the subsample conversion rate that is applied when unpacking pixel data. The accepted param values are GL_PIXEL_SUBSAMPLE_4444_SGIX, GL_PIXEL_SUBSAMPLE_2424_SGIX, and GL_PIXEL_SUBSAMPLE_4242_SGIX. When set to other than the default GL_PIXEL_SUBSAMPLE_4444_SGIX value, pixel groups are upsampled to produce RGB or RGBA component groups, depending on the source format. The packed subsampled source pixel is composed of two values, and the width argument to the pixel routine must be a multiple of 2 pixels. The unpacked pixel group is composed of R, G, and B components in the order specified by the format. When a 4- component format is specified, an alpha component is added to the unpacked group and set to the maximum clamped value of the source type. Pixel group values are also affected by the state of the GL_UNPACK_RESAMPLE_SGIX mode. Subsampled pixel pairs are unpacked as follows: 2424 - replicate : 2424 - zero-fill : <P00,P01> <P10,P11> <P00,P01> <P10,P11> | | | | | | | | | | o-----o---+---o | | o-----o | | | | | | | | | | o---+---+-----o | | | | | 0.0 | 0.0 | | | | | | | | | | | | V V V V V V V V V V V V <U00,U01,U02> <U10,U11,U12> <U00,U01,U02> <U10,U11,U12> 4242 - replicate : 4242 - zero-fill : <P00,P01> <P10,P11> <P00,P01> <P10,P11> | | __\ __|_ | | __\ __| \ / \____ / \ \ \ / / \ X X__ \ \ X / \ / \ / \ \ | / \ / 0.0 \ 0.0 | | | | | | | | | | | | V V V V V V V V V V V V <U00,U01,U02> <U10,U11,U12> <U00,U01,U02> <U10,U11,U12> GL_UNPACK_RESAMPLE_SGIX Specifies the resample mode in effect when an unpack subsample rate is being applied. The accepted param values are GL_RESAMPLE_REPLICATE_SGIX and GL_RESAMPLE_ZERO_FILL_SGIX. When GL_RESAMPLE_ZERO_FILL_SGIX is selected, the lower-rate sampled components in the second group of each pixel pair are assigned a zero value. Otherwise the lower-rate components replicate corresponding values from the preceding unpacked group. The following table gives the type, initial value, and range of valid values for each storage parameter that can be set with fglPixelStore. pname Type Initial Value Valid Range GL_PACK_SWAP_BYTES boolean false true or false GL_PACK_LSB_FIRST boolean false true or false GL_PACK_ROW_LENGTH integer 0 [0,oo) GL_PACK_IMAGE_HEIGHT integer 0 [0,oo) GL_PACK_IMAGE_DEPTH_SGIS integer 0 [0,oo) GL_PACK_SKIP_ROWS integer 0 [0,oo) GL_PACK_SKIP_PIXELS integer 0 [0,oo) GL_PACK_SKIP_IMAGES integer 0 [0,oo) GL_PACK_SKIP_VOLUMES_SGIS integer 0 [0,oo) GL_PACK_ALIGNMENT integer 4 1, 2, 4, or 8 GL_PACK_SUBSAMPLE_RATE_SGIX enum 4444 4444, 2424, or 4242 GL_PACK_RESAMPLE_SGIX enum decimate decimate GL_UNPACK_SWAP_BYTES boolean false true or false GL_UNPACK_LSB_FIRST boolean false true or false GL_UNPACK_ROW_LENGTH integer 0 [0,oo) GL_UNPACK_IMAGE_HEIGHT integer 0 [0,oo) GL_UNPACK_IMAGE_DEPTH_SGIS integer 0 [0,oo) GL_UNPACK_SKIP_ROWS integer 0 [0,oo) GL_UNPACK_SKIP_PIXELS integer 0 [0,oo) GL_UNPACK_SKIP_IMAGES integer 0 [0,oo) GL_UNPACK_SKIP_VOLUMES_SGIS integer 0 [0,oo) GL_UNPACK_ALIGNMENT integer 4 1, 2, 4, or 8 GL_UNPACK_SUBSAMPLE_RATE_SGIX enum 4444 4444, 2424, or 4242 GL_UNPACK_RESAMPLE_SGIX enum replicate replicate or zero-fill fglPixelStoref can be used to set any pixel store parameter. If the parameter type is boolean, then if param is 0, the parameter is false; otherwise it is set to true. If pname is a integer type parameter, param is rounded to the nearest integer. Likewise, fglPixelStorei can also be used to set any of the pixel store parameters. Boolean parameters are set to false if param is 0 and true otherwise. NOTES The pixel storage modes in effect when fglDrawPixels, fglReadPixels, fglTexImage1D, fglTexImage2D, fglTexImage3D, fglTexImage4DSGIS, fglTexSubImage1D, fglTexSubImage2D, fglTexSubImage3D, fglTexSubImage4DSGIS, fglBitmap, or fglPolygonStipple is placed in a display list control the interpretation of memory data. Likewise, if the GL_ARB_imaging extension is supported, the pixel storage modes in effect when fglColorTable, fglColorSubTable, fglConvolutionFilter1D, fglConvolutionFilter2D, of fglSeparableFilter2D is placed in a display list control the intrepretation of memory data. The pixel storage modes in effect when a display list is executed are not significant. Pixel storage modes are client state and must be pushed and restored using fglPushClientAttrib and fglPopClientAttrib. ERRORS GL_INVALID_ENUM is generated if pname is not an accepted value. GL_INVALID_VALUE is generated if a negative row length, pixel skip, or row skip value is specified, or if alignment is specified as other than 1, 2, 4, or 8, or if subsample rate or resample is specified with a value that is not accepted. GL_INVALID_OPERATION is generated if fglPixelStore is executed between the execution of fglBegin and the corresponding execution of fglEnd. ASSOCIATED GETS fglGet with argument GL_PACK_SWAP_BYTES fglGet with argument GL_PACK_LSB_FIRST fglGet with argument GL_PACK_ROW_LENGTH fglGet with argument GL_PACK_IMAGE_HEIGHT fglGet with argument GL_PACK_IMAGE_DEPTH_SGIS fglGet with argument GL_PACK_SKIP_ROWS fglGet with argument GL_PACK_SKIP_PIXELS fglGet with argument GL_PACK_SKIP_IMAGES fglGet with argument GL_PACK_SKIP_VOLSUME_SGIS fglGet with argument GL_PACK_ALIGNMENT fglGet with argument GL_PACK_SUBSAMPLE_RATE_SGIX fglGet with argument GL_PACK_RESAMPLE_SGIX fglGet with argument GL_UNPACK_SWAP_BYTES fglGet with argument GL_UNPACK_LSB_FIRST fglGet with argument GL_UNPACK_ROW_LENGTH fglGet with argument GL_UNPACK_IMAGE_HEIGHT fglGet with argument GL_UNPACK_IMAGE_DEPTH_SGIS fglGet with argument GL_UNPACK_SKIP_ROWS fglGet with argument GL_UNPACK_SKIP_PIXELS fglGet with argument GL_UNPACK_SKIP_IMAGES fglGet with argument GL_UNPACK_SKIP_VOLUMES_SGIS fglGet with argument GL_UNPACK_ALIGNMENT fglGet with argument GL_UNPACK_SUBSAMPLE_RATE_SGIX fglGet with argument GL_UNPACK_RESAMPLE_SGIX MACHINE DEPENDENCIES 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 fglBitmap, fglColorTable, fglColorSubTable, fglConvolutionFilter1D, fglConvolutionFilter2D, fglSeparableFilter2D, fglDrawPixels, fglHistogram, fglMinmax, fglPixelMap, fglPixelTransfer, fglPixelZoom, fglPolygonStipple, fglPushClientAttrib, fglReadPixels, fglTexImage1D, fglTexImage2D, fglTexImage3D, fglTexImage4DSGIS, fglTexSubImage1D, fglTexSubImage2D, fglTexSubImage3D, fglTexSubImage4DSGIS