| XXX - Not complete. |
| |
| Name |
| |
| SGIX_resample |
| |
| Name Strings |
| |
| GL_SGIX_resample |
| |
| Version |
| |
| Last Modified Date: January 27, 2015 |
| Revision: 2 |
| |
| Number |
| |
| 212 |
| |
| Dependencies |
| |
| SGIX_subsample affects the definition of this extension |
| EXT_texture3D affects the definition of this extension |
| EXT_subtexture affects the definition of this extension |
| EXT_histogram affects the definition of this extension |
| EXT_convolution affects the definition of this extension |
| SGI_color_table affects the definition of this extension |
| |
| Overview |
| |
| This extension enhances the unpacking resampling capabilities |
| of the SGIX_subsample extension. |
| |
| When pixel data is received from the client and an unpacking |
| upsampling mode other than PIXEL_SUBSAMPLE_RATE_4444_SGIX is |
| specified, the upsampling is performed via one of two methods: |
| RESAMPLE_REPLICATE_SGIX, RESAMPLE_ZERO_FILL_SGIX. |
| Replicate and zero fill are provided to |
| give the application greatest performance and control over the |
| filtering process. |
| |
| However, when pixel data is read back to the client and a |
| packing downsampling mode other than PIXEL_SUBSAMPLE_RATE_4444_SGIX |
| is specified, downsampling is |
| performed via simple component decimation (point sampling). That is, |
| only the RESAMPLE_DECIMATE_SGIX is valid. |
| |
| |
| Issues |
| |
| * this spec omits the packing downsampling mode. But I think |
| we will have to address it at some point, so I'm adding the |
| RESAMPLE_DECIMATE_SGIX as another tag to complement the unpacking |
| resample modes. |
| |
| * In the public Khronos spec files and headers, these values |
| used to be used for some of the tokens: |
| |
| #define GL_PACK_RESAMPLE_SGIX 0x842C |
| #define GL_UNPACK_RESAMPLE_SGIX 0x842D |
| #define GL_RESAMPLE_REPLICATE_SGIX 0x842E |
| #define GL_RESAMPLE_ZERO_FILL_SGIX 0x842F |
| #define GL_RESAMPLE_DECIMATE_SGIX 0x8430 |
| |
| These values corresponded to the internal SGI spec files and |
| (probably) to what was shipped on SGI IRIX systems supporting this |
| extension, but the spec was always inconsistent with these values. |
| Since SGI is long out of the graphics business, in order to reduce |
| incompatibility between tools pulling from the Khronos spec file |
| and tools pulling from the extension spec, the spec file has been |
| changed to match the extension. |
| |
| New Procedures and Functions |
| |
| None. |
| |
| New Tokens |
| |
| Accepted by the <pname> parameter of PixelStoref, PixelStorei, |
| GetBooleanv, GetIntegerv, GetFloatv and GetDoublev: |
| |
| PACK_RESAMPLE_SGIX 0x842E |
| UNPACK_RESAMPLE_SGIX 0x842F |
| |
| |
| Accepted by the <param> parameter of PixelStoref and |
| PixelStorei when the <pname> parameter is UNPACK_RESAMPLE_SGIX: |
| |
| RESAMPLE_REPLICATE_SGIX 0x8433 |
| RESAMPLE_ZERO_FILL_SGIX 0x8434 |
| |
| Accepted by the <param> parameter of PixelStoref and |
| PixelStorei when the <pname> parameter is PACK_RESAMPLE_SGIX: |
| |
| RESAMPLE_DECIMATE_SGIX 0x8430 |
| |
| |
| Additions to Chapter 2 of the 1.1 Specification (OpenGL Operation) |
| |
| None. |
| |
| Additions to Chapter 3 of the 1.1 Specification (Rasterization) |
| |
| 3.6.1 Pixel Storage Modes |
| |
| The following is added to Table 3.1: |
| |
| Parameter Name Type Initial Value Valid Range |
| -------------- ---- ------------- ----------- |
| UNPACK_RESAMPLE_SGIX integer RESAMPLE_REPLICATE_SGIX RESAMPLE_REPLICATE_SGIX |
| RESAMPLE_ZERO_FILL_SGIX |
| |
| PACK_RESAMPLE_SGIX integer RESAMPLE_DECIMATE_SGIX RESAMPLE_DECIMATE_SGIX |
| |
| |
| 3.6.3 Rasterization of Pixel Rectangles |
| |
| |
| <In the new section which is inserted before "Conversion to RGB", append> |
| |
| Conversion to Uniform Sampling |
| ------------------------------ |
| |
| This step is applied only if the PixelStore parameter |
| UNPACK_SUBSAMPLE_RATE_SGIX is set to something other than |
| PIXEL_SUBSAMPLE_RATE_4444_SGIX. If UNPACK_SUBSAMPLE_RATE_SGIX is set to |
| PIXEL_SUBSAMPLE_RATE_2424_SGIX or PIXEL_SUBSAMPLE_RATE_4242_SGIX then |
| the number of components per pixel is increased from two to three. |
| After upsampling, the data is treated as though it were RGB. When |
| this step is carried out the operation is controlled by the value |
| of the PixelStore parameter UNPACK_RESAMPLE_SGIX. |
| |
| If UNPACK_RESAMPLE_SGIX is set to RESAMPLE_REPLICATE_SGIX then the first |
| component of the ith resulting pixel in a row is taken from the |
| first component of input pixel 2*floor(i/2). The second |
| component is taken from ith pixel. The third component is taken |
| from the first component of input pixel 2*floor(i/2)+1. In the |
| 4224 case, the fourth component is taken from the third |
| component of each input pixel. This process is fully described |
| in the SGIX_subsample spec. |
| |
| If the PixelStore parameter UNPACK_RESAMPLE_SGIX is set to |
| RESAMPLE_ZERO_FILL_SGIX then derived components are zeroed. Note that |
| subsampled components are co-sited with even numbered pixels, |
| and the odd numbered pixels produced have the zeroed components: |
| |
| 2424: |
| |
| <L0,A0> <L1,A1> <L2,A2> <L3,A3> |
| <Cb0,Y0> <Cr0,Y1> <Cb2,Y2> <Cr2, Y3> |
| | | | | | | | | |
| | | o-----o | | | o-----o | |
| | | | | | | | | |
| | | | 0.0 | 0.0 | | | 0.0 | 0.0 |
| | | | | | | | | | | | | |
| V V V V V V V V V V V V |
| <Cb0,Y0,Cr0> <Cb0,Y1,Cr0> <Cb2,Y2,Cr2> <Cb2,Y3,Cr2> |
| < R0,G0,B1 > < R0,G1,B1 > < R2,G2,B3 > < R2,G3,B3 > |
| |
| 4242: |
| < A0,L0> <A1,L1 > <A2,L2 > < A3,L3 > |
| <Y0,Cb0> <Y1,Cr0> <Y2,Cb2> <Y3,Cr2> |
| | | | | | | | | |
| \ / __\__/ \ / __\__/ |
| X ___/ \ X ___/ \ |
| / \ / 0.0 \ 0.0 / \ / 0.0 \ 0.0 |
| | | | | | | | | | | | | |
| V V V V V V V V V V V V |
| <Cb0,Y0,Cr0> <Cb0,Y1,Cr0> <Cb2,Y2,Cr2> <Cb2,Y3,Cr2> |
| < R0,G0,B1 > < R0,G1,B1 > < R2,G2,B3 > < R2,G3,B3 > |
| |
| |
| Note that the <width> parameter to DrawPixels should be even, |
| as should the value of UNPACK_SKIP_PIXELS, and |
| UNPACK_ROW_LENGTH. If any of these are odd then the error |
| INVALID_OPERATION is issued. |
| |
| |
| Additions to Chapter 4 of the 1.1 Specification (Per-Fragment |
| Operations and the Frame Buffer) |
| |
| None. |
| |
| Additions to Chapter 5 of the 1.1 Specification (Special Functions) |
| |
| None. |
| |
| Additions to Chapter 6 of the 1.1 Specification (State and State Requests) |
| |
| XXX |
| |
| Additions to the GLX Specification |
| |
| |
| Errors |
| |
| XXX |
| |
| |
| New State |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| UNPACK_RESAMPLE_SGIX GetIntegerv Z4 RESAMPLE_REPLICATE_SGIX client |
| PACK_RESAMPLE_SGIX GetIntegerv Z4 RESAMPLE_REPLICATE_SGIX client |
| |
| New Implementation Dependent State |
| |
| None. |
| |
| Revision History |
| |
| Revision 1, July 27, 1999 - SGI internal revision #4. |
| |
| Revision 2, January 27, 2015 - note that Khronos spec file values from |
| enums have been changed to match the extension spec (Khronos internal |
| bug 12653). |
