Queries of value TEXTURE WIDTH, TEXTURE HEIGHT, TEXTURE DEPTH, and

TEXTURE BORDER return the width, height, depth, and border as specified when the image array was created. The internal format of the image array is queried as TEXTURE INTERNAL FORMAT, or as TEXTURE COMPONENTS for compatibility with GL version 1.0.

For GetPixelMap, the map must be a map name from table 3.3. For GetMap, map must be one of the map types described in section 5.1, and value must be one of ORDER, COEFF, or DOMAIN.

6.1.4 Texture Queries

The command

void GetTexImage( enum tex, int lod, enum format, enum type, void *img );

is used to obtain texture images. It is somewhat different from the other get commands; tex is a symbolic value indicating which texture (or texture face in the case of a cube map texture target name) is to be obtained. TEXTURE 1D, TEXTURE 2D, and TEXTURE 3D indicate a one-, two-, or three-dimensional texture respectively,

TEXTURE CUBE MAP POSITIVE Z, and TEXTURE CUBE MAP NEGATIVE Z indicate the respective face of a cube map texture. lod is a level-of-detail number, format is a pixel format from table 3.6, type is a pixel type from table 3.5, and img is a pointer to a block of memory.

GetTexImage obtains component groups from a texture image with the indicated level-of-detail. The components are assigned among R, G, B, and A according to table 6.1, starting with the first group in the first row, and continuing by obtaining groups in order from each row and proceeding from the first row to the last, and from the first image to the last for three-dimensional textures. These groups are then packed and placed in client memory. No pixel transfer operations are performed on this image, but pixel storage modes that are applicable to ReadPixels are applied.

For three-dimensional textures, pixel storage operations are applied as if the image were two-dimensional, except that the additional pixel storage state values PACK IMAGE HEIGHT and PACK SKIP IMAGES are applied. The correspondence of texels to memory locations is as defined for TexImage3D in section 3.8.1.

The row length, number of rows, image depth, and number of images are determined by the size of the texture image (including any borders). Calling GetTexImage with lod less than zero or larger than the maximum allowable causes

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Table 6.1: Texture, table, and filter return values. Ri, Gi, Bi, Ai, Li, and Ii are components of the internal format that are assigned to pixel values R, G, B, and A. If a requested pixel value is not present in the internal format, the specified constant value is used.

the error INVALID VALUE Calling GetTexImage with format of COLOR INDEX,

STENCIL INDEX, or DEPTH COMPONENT causes the error INVALID ENUM. The command

void GetCompressedTexImage( enum target, int lod, void *img );

is used to obtain texture images stored in compressed form. The parameters target, lod, and img are interpreted in the same manner as in GetTexImage. When called,

GetCompressedTexImage writes TEXTURE COMPRESSED IMAGE SIZE ubytes of compressed image data to the memory pointed to by img. The compressed image data is formatted according to the definition of the texture’s internal format. All pixel storage and pixel transfer modes are ignored when returning a compressed texture image.

Calling GetCompressedTexImage with an lod value less than zero or greater than the maximum allowable causes an INVALID VALUE error. Calling GetCompressedTexImage with a texture image stored with an uncompressed internal format causes an INVALID OPERATION error.

The command

boolean IsTexture( uint texture );

returns TRUE if texture is the name of a texture object. If texture is zero, or is a nonzero value that is not the name of a texture object, or if an error condition occurs, IsTexture returns FALSE. A name returned by GenTextures, but not yet bound, is not the name of a texture object.

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6.1.5 Stipple Query

The command

void GetPolygonStipple( void *pattern );

obtains the polygon stipple. The pattern is packed into memory according to the procedure given in section 4.3.2 for ReadPixels; it is as if the height and width passed to that command were both equal to 32, the type were BITMAP, and the format were COLOR INDEX.

6.1.6 Color Matrix Query

stack is returned by GetFloatv called with pname set to COLOR MATRIX or TRANSPOSE COLOR MATRIX. The depth of the color matrix stack, and the maximum depth of the color matrix stack, are queried with GetIntegerv, setting pname to COLOR MATRIX STACK DEPTH and MAX COLOR MATRIX STACK DEPTH respectively.

6.1.7 Color Table Query

The current contents of a color table are queried using

void GetColorTable( enum target, enum format, enum type, void *table );

target must be one of the regular color table names listed in table 3.4. format and type accept the same values as do the corresponding parameters of GetTexImage. The one-dimensional color table image is returned to client memory starting at table. No pixel transfer operations are performed on this image, but pixel storage modes that are applicable to ReadPixels are performed. Color components that are requested in the specified format, but which are not included in the internal format of the color lookup table, are returned as zero. The assignments of internal color components to the components requested by format are described in table 6.1.

The functions

void GetColorTableParameter{if}v( enum target, enum pname, T params );

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or COLOR TABLE INTENSITY SIZE. The value of the specified parameter is returned in params.

6.1.8 Convolution Query

The current contents of a convolution filter image are queried with the command

void GetConvolutionFilter( enum target, enum format, enum type, void *image );

target must be CONVOLUTION 1D or CONVOLUTION 2D. format and type accept the same values as do the corresponding parameters of GetTexImage. The onedimensional or two-dimensional images is returned to client memory starting at image. Pixel processing and component mapping are identical to those of GetTexImage.

The current contents of a separable filter image are queried using

void GetSeparableFilter( enum target, enum format, enum type, void *row, void *column, void *span );

target must be SEPARABLE 2D. format and type accept the same values as do the corresponding parameters of GetTexImage. The row and column images are returned to client memory starting at row and column respectively. span is currently unused. Pixel processing and component mapping are identical to those of GetTexImage.

The functions

void GetConvolutionParameter{if}v( enum target,

MAX CONVOLUTION WIDTH, or MAX CONVOLUTION HEIGHT. The value of the specified parameter is returned in params.

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