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Name
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ANGLE_get_image
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Name Strings
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GL_ANGLE_get_image
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Contributors
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Jamie Madill
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Contact
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Jamie Madill (jmadill 'at' google.com)
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Notice
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Copyright (c) 2019 The Khronos Group Inc. Copyright terms at
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http://www.khronos.org/registry/speccopyright.html
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Status
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Draft
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Version
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Version 1, October 21, 2019
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Number
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OpenGL ES Extension #??
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Dependencies
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Requires OpenGL ES 2.0
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Written against the OpenGL ES 3.2 specification.
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Overview
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This extension allows the OpenGL application to query and read back Texture
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and Renderbuffer pixel data. The OpenGL context exposes new queries for the
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implementation pixel format and type similar to glReadPixels. The context
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also exposes new commands to read back pixel data with these parameters.
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New Procedures and Functions
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void GetTexImageANGLE(GLenum target, GLint level, GLenum format, GLenum type,
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void *pixels);
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void GetRenderbufferImageANGLE(GLenum target, GLint level, GLenum format,
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GLenum type, void *pixels);
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New Tokens
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None
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Additions to the OpenGL ES Specification
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Update section 8.11.2 "Texture Parameter Queries":
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Change "<pname> must be one of IMAGE_FORMAT_COMPATIBILITY_TYPE, TEXTURE_-
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IMMUTABLE_FORMAT, TEXTURE_IMMUTABLE_LEVELS, or one of the symbolic
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values in table 8.19." to "<pname> must be one of IMAGE_FORMAT_COMPATIBILITY_-
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TYPE, TEXTURE_IMMUTABLE_FORMAT, TEXTURE_IMMUTABLE_LEVELS, IMPLEMENTATION_-
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COLOR_READ_TYPE, IMPLEMENTATION_COLOR_READ_FORMAT or one of the symbolic
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values in table 8.19.".
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Add a paragrah: "Querying <pname> with IMPLEMENTATION_COLOR_READ_TYPE or
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IMPLEMENTATION_COLOR_READ_FORMAT returns the implementation-dependent read
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format and type for use with GetTexImageANGLE."
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Update section 9.2.6 "Renderbuffer Object Queries":
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Add a paragraph: "If <pname> is IMPLEMENTATION_COLOR_READ_TYPE or
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IMPLEMENTATION_COLOR_READ_FORMAT then <params> will contain the
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implementation-dependent read format and type for use with
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GetRenderbufferImageANGLE."
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Add a section "Texture and Renderbuffer Image Queries":
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Texture and Renderbuffer images may be obtained from a Texture or
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Renderbuffer with the commands
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void GetTexImageANGLE(GLenum target, GLint level, GLenum format, GLenum type,
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void *pixels);
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void GetRenderbufferImageANGLE(GLenum target, GLenum format, GLenum type,
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void *pixels);
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For GetTexImageANGLE, <target> specifies the target to which the texture
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object is bound. target must be one of TEXTURE_2D, TEXTURE_3D,
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TEXTURE_2D_ARRAY, TEXTURE_CUBE_MAP_ARRAY, indicating a two- or three-
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dimensional, two-dimensional array, cube map array respectively. <target>
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may also be one of the targets from table 8.20, indicating the
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corresponding face of a cube map texture.
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For GetRenderbufferImageANGLE, <target> must be RENDERBUFFER.
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<level> is a level-of-detail number, <format> is a pixel format from table 8.5,
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and <type> is a pixel type from table 8.4.
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These commands obtain component groups from a texture or renderbuffer image
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with the indicated level-of-detail. If <format> is a color format then the
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components are assigned among R, G, B, and A, starting with the first group
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in the first row, and continuing by obtaining groups in order from each row
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and proceeding from the first row to the last, and from the first image to
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the last for three-dimensional textures. Two-dimensional array and cube map
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array textures are treated as three-dimensional images, where the layers are
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treated as rows or images. Cube map textures are treated as three-dimensional
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images with a depth of 6, where the cube map faces are ordered as image layers
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as shown in table 8.24.
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If <format> is DEPTH_COMPONENT, DEPTH_STENCIL, or STENCIL_INDEX, then
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each depth component and/or stencil index is assigned with the same ordering of
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rows and images.
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These groups are then packed and placed in client or pixel buffer object memory.
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If a pixel pack buffer is bound (as indicated by a non-zero value of PIXEL_-
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PACK_BUFFER_BINDING), <pixels> is an offset into the pixel pack buffer;
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otherwise, <pixels> is a pointer to client memory. Pixel storage modes that are
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applicable to ReadPixels are applied, as described in table 16.1 and section
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16.1.2.
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For three-dimensional, two-dimensional array, cube map array, and cube map
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textures pixel storage operations are applied as if the image were two-
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dimensional, except that the additional pixel storage state values
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PACK_IMAGE_HEIGHT and PACK_SKIP_IMAGES are applied. The correspondence of texels
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to memory locations is as defined for TexImage3D in section 8.5.
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The row length, number of rows, image depth, and number of images are determined
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by the size of the texture or renderbuffer image (including any borders).
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Errors:
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An INVALID_ENUM error is generated by GetTexImage if <target> is
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not one of TEXTURE_2D, TEXTURE_3D, TEXTURE_2D_ARRAY, TEXTURE_CUBE_MAP_ARRAY,
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or one of the targets from table 8.20.
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An INVALID_ENUM error is generated by GetRenderbufferImage is <target> is not
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RENDERBUFFER.
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An INVALID_VALUE error is generated if <level> is negative or larger than
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the maximum allowable level.
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An INVALID_OPERATION error is generated if any of the following mismatches
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between <format> and the internal format of the texture or renderbuffer image
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exist:
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* <format> is a color format (one of the formats in table 8.3 whose target is
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the color buffer) and the base internal format of the texture or renderbuffer
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image is not a color format.
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* <format> is DEPTH_COMPONENT and the base internal format is not
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DEPTH_COMPONENT or DEPTH_STENCIL.
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* <format> is DEPTH_STENCIL and the base internal format is not DEPTH_-
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STENCIL.
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* <format> is STENCIL_INDEX and the base internal format is not
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STENCIL_INDEX or DEPTH_STENCIL.
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* <format> is one of the integer formats in table 8.5 and the internal format
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of the texture or renderbuffer image is not integer, or <format> is not one
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of the integer formats in table 8.5 and the internal format is integer.
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An INVALID_OPERATION error is generated if a pixel pack buffer object
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is bound and packing the texture or renderbuffer image into the buffer’s
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memory would exceed the size of the buffer.
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An INVALID_OPERATION error is generated if a pixel pack buffer object
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is bound and <pixels> is not evenly divisible by the number of basic machine
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units needed to store in memory the GL data type corresponding to type (see
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table 8.4).
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Dependencies on ARB_texture_rectangle
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TEXTURE_RECTANGLE is accepted by GetTexImageANGLE and GetRenderbufferImageANGLE.
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An INVALID_VALUE error is generated if <level> is non-zero and the effective
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<target> is TEXTURE_RECTANGLE.
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New State
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Add to table 21.10 "Textures (state per texture object)":
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Get Value Type Get Command Initial Value Description Section
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-------------------------------- ---- ----------- ------------- --------------------------- -------
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IMPLEMENTATION_COLOR_READ_FORMAT E GetTextureParameteriv empty Implementation pixel format 8.11.2
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IMPLEMENTATION_COLOR_READ_TYPE E GetTextureParameteriv empty Implementation pixel type 8.11.2
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Add to table 21.17 "Renderbuffer (state per renderbuffer object)":
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Get Value Type Get Command Initial Value Description Section
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-------------------------------- ---- ----------- ------------- --------------------------- -------
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IMPLEMENTATION_COLOR_READ_FORMAT E GetRenderbufferParameteriv empty Implementation pixel format 9.2.6
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IMPLEMENTATION_COLOR_READ_TYPE E GetRenderbufferParameteriv empty Implementation pixel type 9.2.6
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Issues
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1) Should GetTexImageANGLE/GetRenderbufferImageANGLE only accept IMPLEMENTATION-
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_COLOR_READ_FORMAT/TYPE or should they behave the same as GetTexImage in GL?
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Resolved: Keep the spec wording closer to the desktop GL version. It should
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not involve much additional implementation work except for validation.
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Revision History
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Rev. Date Author Changes
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---- ------------- --------- ----------------------------------------
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1 Oct 24, 2019 jmadill Initial version
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