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glman函数说明 glman函数说明 glman函数说明

	  <STRONG>GL_RGB</STRONG>    Each element is an RGB triple.  The	GL converts it
		    to floating	point and assembles it into an RGBA
		    element by attaching 1 for alpha.  Each component
		    is then multiplied by the signed scale factor
		    <STRONG>GL_c_SCALE</STRONG>,	added to the signed bias <STRONG>GL_c_BIAS</STRONG>,
		    and	clamped	to the range [0,1] (see
		    <STRONG>glPixelTransfer</STRONG>).

	  <STRONG>GL_RGBA</STRONG>   Each element contains all four components.	Each
		    component is multiplied by the signed scale	factor
		    <STRONG>GL_c_SCALE</STRONG>,	added to the signed bias <STRONG>GL_c_BIAS</STRONG>,
		    and	clamped	to the range [0,1] (see
		    <STRONG>glPixelTransfer</STRONG>).

	  <STRONG>GL_LUMINANCE</STRONG>
		    Each element is a single luminance value.  The GL
		    converts it	to floating point, then	assembles it
		    into an RGBA element by replicating	the luminance
		    value three	times for red, green, and blue and
		    attaching 1	for alpha. Each	component is then
		    multiplied by the signed scale factor <STRONG>GL_c_SCALE</STRONG>,
		    added to the signed	bias <STRONG>GL_c_BIAS</STRONG>,	and clamped to
		    the	range [0,1] (see <STRONG>glPixelTransfer</STRONG>).

	  <STRONG>GL_LUMINANCE_ALPHA</STRONG>
		    Each element is a luminance/alpha pair.  The GL
		    converts it	to floating point, then	assembles it
		    into an RGBA element by replicating	the luminance
		    value three	times for red, green, and blue.	 Each
		    component is then multiplied by the	signed scale
		    factor <STRONG>GL_c_SCALE</STRONG>, added to	the signed bias
		    <STRONG>GL_c_BIAS</STRONG>, and clamped to the range	[0,1] (see
		    <STRONG>glPixelTransfer</STRONG>).

	  Refer	to the <STRONG>glDrawPixels</STRONG> reference page for a description
	  of the acceptable values for the <EM>type</EM>	parameter.

	  If an	application wants to store the texture at a certain
	  resolution or	in a certain format, it	can request the
	  resolution and format	with <EM>internalformat</EM>. The GL will
	  choose an internal representation that closely approximates
	  that requested by <EM>internalformat</EM>, but	it may not match
	  exactly.  (The representations specified by <STRONG>GL_LUMINANCE</STRONG>,
	  <STRONG>GL_LUMINANCE_ALPHA</STRONG>, <STRONG>GL_RGB</STRONG>, and <STRONG>GL_RGBA</STRONG> must match exactly.
	  The numeric values 1,	2, 3, and 4 may	also be	used to
	  specify the above representations.)

	  Use the <STRONG>GL_PROXY_TEXTURE_2D</STRONG> target to	try out	a resolution
	  and format. The implementation will update and recompute its
	  best match for the requested storage resolution and format.
	  To then query	this state, call <STRONG>glGetTexLevelParameter</STRONG>.  If
	  the texture cannot be	accommodated, texture state is set to
	  0.

	  A one-component texture image	uses only the red component of
	  the RGBA color extracted from	<EM>pixels</EM>.	A two-component	image
	  uses the R and A values.  A three-component image uses the
	  R, G,	and B values.  A four-component	image uses all of the
	  RGBA components.

     <STRONG>NOTES</STRONG>
	  Texturing has	no effect in color index mode.

	  The texture image can	be represented by the same data
	  formats as the pixels	in a <STRONG>glDrawPixels</STRONG> command, except that
	  <STRONG>GL_STENCIL_INDEX</STRONG> and <STRONG>GL_DEPTH_COMPONENT</STRONG> cannot be used.
	  <STRONG>glPixelStore</STRONG> and <STRONG>glPixelTransfer</STRONG> modes affect	texture	images
	  in exactly the way they affect <STRONG>glDrawPixels</STRONG>.

	  <STRONG>glTexImage2D</STRONG> and <STRONG>GL_PROXY_TEXTURE_2D</STRONG> are only	available if
	  the GL version is 1.1	or greater.

	  Internal formats other than 1, 2, 3, or 4 may	only be	used
	  if the GL version is 1.1 or greater.

	  In GL	version	1.1 or greater,	<EM>pixels</EM> may be a	null pointer.
	  In this case texture memory is allocated to accommodate a
	  texture of width <EM>width</EM> and height <EM>height</EM>.  You can then
	  download subtextures to initialize this texture memory. The
	  image	is undefined if	the user tries to apply	an
	  uninitialized	portion	of the texture image to	a primitive.

     <STRONG>ERRORS</STRONG>
	  <STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>target</EM> is not	<STRONG>GL_TEXTURE_2D</STRONG>
	  or <STRONG>GL_PROXY_TEXTURE_2D</STRONG>.

	  <STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>format</EM> is not	an accepted
	  format constant.  Format constants other than
	  <STRONG>GL_STENCIL_INDEX</STRONG> and <STRONG>GL_DEPTH_COMPONENT</STRONG> are accepted.

	  <STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>type</EM> is not a	type constant.

	  <STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>type</EM> is <STRONG>GL_BITMAP</STRONG> and	<EM>format</EM>
	  is not <STRONG>GL_COLOR_INDEX</STRONG>.

	  <STRONG>GL_INVALID_VALUE</STRONG> is generated	if <EM>level</EM> is less than 0.

	  <STRONG>GL_INVALID_VALUE</STRONG> may be generated if <EM>level</EM> is	greater	than
	  log <EM>max</EM>, where <EM>max</EM> is	the returned value of
	  <STRONG>GL_MAX_TEXTURE_SIZE</STRONG>.

	  <STRONG>GL_INVALID_VALUE</STRONG> is generated	if <EM>internalformat</EM> is not 1, 2,
	  3, 4,	or one of the accepted resolution and format symbolic
	  constants.

	  <STRONG>GL_INVALID_VALUE</STRONG> is generated	if <EM>width</EM> or <EM>height</EM> is less
	  than 0 or greater than 2 + <STRONG>GL_MAX_TEXTURE_SIZE</STRONG>, or if	either
	  cannot be represented	as 2k+2(border)	for some integer value
	  of <EM>k</EM>.

	  <STRONG>GL_INVALID_VALUE</STRONG> is generated	if <EM>border</EM> is not 0 or 1.

	  <STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>glTexImage2D</STRONG> is
	  executed between the execution of <STRONG>glBegin</STRONG> and	the
	  corresponding	execution of <STRONG>glEnd</STRONG>.

     <STRONG>ASSOCIATED</STRONG>	<STRONG>GETS</STRONG>
	  <STRONG>glGetTexImage</STRONG>
	  <STRONG>glIsEnabled</STRONG> with argument <STRONG>GL_TEXTURE_2D</STRONG>

     <STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
	  <STRONG>glCopyPixels</STRONG>,	<STRONG>glCopyTexImage1D</STRONG>, <STRONG>glCopyTexImage2D</STRONG>,
	  <STRONG>glCopyTexSubImage1D</STRONG>, <STRONG>glCopyTexSubImage2D</STRONG>, <STRONG>glDrawPixels</STRONG>,
	  <STRONG>glPixelStore</STRONG>,	<STRONG>glPixelTransfer</STRONG>, <STRONG>glTexEnv</STRONG>, <STRONG>glTexGen</STRONG>,
	  <STRONG>glTexImage1D</STRONG>,	<STRONG>glTexSubImage1D</STRONG>, <STRONG>glTexSubImage2D</STRONG>,
	  <STRONG>glTexParameter</STRONG>




























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