Name
gl.CopyTexSubImage -- copy a two-dimensional texture subimage
Synopsis
gl.CopyTexSubImage(level, x, y, xoffset, width[, yoffset, height])
Function
gl.CopyTexSubImage() replaces a rectangular portion of a one- or two-dimensional texture image with pixels from the current #GL_READ_BUFFER (rather than from main memory, as is the case for gl.TexSubImage2D()). If the last two arguments are omitted, a rectangular portion of a one-dimension texture image is replaced, otherwise a two-dimensional texture image is the target.

The screen-aligned pixel rectangle with lower left corner at (x,y) and with width width and height height replaces the portion of the texture array with x indices xoffset through xoffset + width - 1, inclusive, and y indices yoffset through yoffset + height - 1, inclusive, at the mipmap level specified by level.

The pixels in the rectangle are processed exactly as if gl.CopyPixels() had been called, but the process stops just before final conversion. At this point, all pixel component values are clamped to the range [0,1] and then converted to the texture's internal format for storage in the texel array.

The destination rectangle in the texture array may not include any texels outside the texture array as it was originally specified. It is not an error to specify a subtexture with zero width or height, but such a specification has no effect.

If any of the pixels within the specified rectangle of the current #GL_READ_BUFFER are outside the read window associated with the current rendering context, then the values obtained for those pixels are undefined.

No change is made to the internalformat, width, height, or border parameters of the specified texture array or to texel values outside the specified subregion.

Texturing has no effect in color index mode.

gl.PixelStore() and gl.PixelTransfer() modes affect texture images in exactly the way they affect gl.DrawPixels().

Please consult an OpenGL reference manual for more information.

Inputs
level
specifies the level-of-detail number; level 0 is the base image level; level n is the nth mipmap reduction image
x
specify the x coordinate of the lower left corner of the rectangular region of pixels to be copied
y
specify the y coordinate of the lower left corner of the rectangular region of pixels to be copied
xoffset
specifies a texel offset in the x direction within the texture array
width
specifies the width of the texture subimage
yoffset
optional: specifies a texel offset in the y direction within the texture array
height
optional: specifies the height of the texture subimage
Errors
#GL_INVALID_OPERATION is generated if the texture array has not been defined by a previous gl.TexImage2D() or gl.CopyTexImage() operation.

#GL_INVALID_VALUE is generated if level is less than 0.

#GL_INVALID_VALUE may be generated if level > log2(max), where max is the returned value of #GL_MAX_TEXTURE_SIZE.

#GL_INVALID_VALUE is generated if xoffset < -b , xoffset + width > w - b , yoffset < -b , or yoffset + height > h -b , where w is the #GL_TEXTURE_WIDTH, h is the #GL_TEXTURE_HEIGHT, and b is the #GL_TEXTURE_BORDER of the texture image being modified. Note that w and h include twice the border width.

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

Associated gets
gl.GetTexImage()

gl.IsEnabled() with argument #GL_TEXTURE_2D or #GL_TEXTURE_1D


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