void glCopyTexSubImage1D(GLenum target, GLint level, GLint xoffset, GLint x, GLint y, GLsizei width);
void glCopyTextureSubImage1D(GLuint texture, GLint level, GLint xoffset, GLint x, GLint y, GLsizei width);
The screen-aligned pixel row with left corner at (x,\ y), and with length width replaces the portion of the texture array with x indices xoffset through xoffset + width - 1, inclusive. The destination in the texture array may not include any texels outside the texture array as it was originally specified.
The pixels in the row are processed exactly as if glReadPixels() 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.
It is not an error to specify a subtexture with zero width, but such a specification has no effect. If any of the pixels within the specified row 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 or width parameters of the specified texture array or to texel values outside the specified subregion.
GL_INVALID_FRAMEBUFFER_OPERATION is generated if the object bound to GL_READ_FRAMEBUFFER_BINDING is not framebuffer complete.
GL_INVALID_OPERATION is generated by glCopyTextureSubImage1D if texture is not the name of an existing texture object, or if the effective target of texture is not GL_TEXTURE_1D.
GL_INVALID_OPERATION is generated if the texture array has not been defined by a previous glTexImage1D(), glCopyTexImage1D(), or glTexStorage1D() operation.
GL_INVALID_VALUE is generated if level is less than 0.
GL_INVALID_VALUE may be generated if level > log 2 max, where max is the returned value of GL_MAX_TEXTURE_SIZE.
GL_INVALID_VALUE is generated if xoffset < 0, or xoffset + width > w, where w is the GL_TEXTURE_WIDTH of the texture image being modified.
GL_INVALID_OPERATION is generated if:
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