gl.PixelStore(pname, param)

pname is a symbolic constant indicating the parameter to be set, and param is the new value. Six of the twelve 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 b0, b1, b2, b3, it is stored in memory as b3, b2, b1, b0 if #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 a certain number of components or indices. See an OpenGL reference manual for details.

#GL_PACK_SKIP_PIXELS

This value is provided as a convenience to the programmer; it provides no functionality that cannot be duplicated simply by incrementing the pointer passed to gl.ReadPixels(). 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.

#GL_PACK_SKIP_ROWS

This value is provided as a convenience to the programmer; it provides no functionality that cannot be duplicated simply by incrementing the pointer passed to gl.ReadPixels(). 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.

#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).

The other six of the twelve storage parameters affect how pixel data is read from client memory. These values are then significant for gl.DrawPixels(), gl.TexImage(), and furthermore also for gl.TexImage1D(), gl.TexImage2D(), gl.TexSubImage(), gl.TexSubImage1D(), gl.TexSubImage2D(), gl.Bitmap(), and gl.PolygonStipple(). 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 b0 , b1 , b2 , b3 , it is taken from memory as b3 , b2 , b1 , b0 if #GL_UNPACK_SWAP_BYTES is true. #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 a certain number of components or indices. See an OpenGL reference manual for details.

#GL_UNPACK_SKIP_PIXELS

This value is provided as a convenience to the programmer; it provides no functionality that cannot be duplicated by incrementing the pointer passed to gl.DrawPixels(), or to gl.TexImage(), or also to gl.TexImage1D() and gl.TexImage2D(), additionally also to gl.TexSubImage(), or to gl.TexSubImage1D() and gl.TexSubImage2D(), gl.Bitmap(), or to gl.PolygonStipple() 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.

#GL_UNPACK_SKIP_ROWS

This value is provided as a convenience to the programmer; it provides no functionality that cannot be duplicated by incrementing the pointer passed to gl.DrawPixels(), or to gl.TexImage(), or also to gl.TexImage1D() and gl.TexImage2D(), additionally also to gl.TexSubImage(), or to gl.TexSubImage1D() and gl.TexSubImage2D(), gl.Bitmap(), or to gl.PolygonStipple() 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.

#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).

The following table gives the type, initial value, and range of valid values for each storage parameter that can be set with gl.PixelStore().

pname | Type | Default | 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_SKIP_ROWS | integer | 0 | [0,oo) #GL_PACK_SKIP_PIXELS | integer | 0 | [0,oo) #GL_PACK_ALIGNMENT | integer | 4 | 1, 2, 4, or 8 #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_SKIP_ROWS | integer | 0 | [0,oo) #GL_UNPACK_SKIP_PIXELS| integer | 0 | [0,oo) #GL_UNPACK_ALIGNMENT | integer | 4 | 1, 2, 4, or 8

The pixel storage modes in effect when gl.DrawPixels(), gl.ReadPixels(), or gl.TexImage(), gl.TexImage1D(), or gl.TexImage2D(), or gl.TexSubImage(), gl.TexSubImage1D(), or also GL's gl.TexSubImage2D(), or gl.Bitmap(), or gl.PolygonStipple() is placed in a display list control the interpretation 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 gl.PushClientAttrib() and gl.PopClientAttrib().

Please consult an OpenGL reference manual for more information.

pname

specifies the symbolic name of the parameter to be set (see above for possible modes)

param

specifies the value that pname is set to

#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.

#GL_INVALID_OPERATION is generated if gl.PixelStore() is executed between the execution of gl.Begin() and the corresponding execution of gl.End().

gl.Get() with argument #GL_PACK_LSB_FIRST

gl.Get() with argument #GL_PACK_ROW_LENGTH

gl.Get() with argument #GL_PACK_SKIP_ROWS

gl.Get() with argument #GL_PACK_SKIP_PIXELS

gl.Get() with argument #GL_PACK_ALIGNMENT

gl.Get() with argument #GL_UNPACK_SWAP_BYTES

gl.Get() with argument #GL_UNPACK_LSB_FIRST

gl.Get() with argument #GL_UNPACK_ROW_LENGTH

gl.Get() with argument #GL_UNPACK_SKIP_ROWS

gl.Get() with argument #GL_UNPACK_SKIP_PIXELS

gl.Get() with argument #GL_UNPACK_ALIGNMENT