Name

    KHR_EGL_image

Name Strings

    VG_KHR_EGL_image

Contributors

    Ruchika Dhingra
    Gary King
    Ignacio Llamas
    Chris Wynn

Contacts

    Gary King, NVIDIA Corporation   (gking 'at' nvidia.com)

Status

    Approved.

Version

    Revision: #4

Number

    OpenVG Extension #1

Dependencies

    Requires OpenVG version 1.0 or later.
 
    Requires EGL 1.2 and the EGL_KHR_image extension.

    This extension is written against the wording of the OpenVG 1.0
    Specification.

Overview

    This extension provides a mechanism for creating derived resources,
    such as VGImages, from EGLImages.

Glossary

    Please see the EGL_KHR_image specification for a definition of terms
    used by this extension.

New Types

    /*
     * VGEGLImageKHR is an opaque handle to an EGLImage
     */
    typedef void* VGeglImageKHR;

New Procedures and Functions

    VGImage CreateEGLImageTargetKHR(VGeglImageKHR image);

New Tokens

    None.

Additions to Chapter 11 of the OpenVG 1.0 Specification (Images)

    In Section 11.3, page 105, add the following text after the
    paragraph defining vgCreateImage:

    "vgCreateEGLImageTargetKHR

      vgCreateEGLImageTarget creates an EGLImage target VGImage
      object from the provided EGLImage <image>.  <image> should be
      of type EGLImageKHR, cast into the type VGeglImageKHR.  Assuming
      no errors are generated in this function, the resulting VGImage
      will be an EGLImage target of the specified EGLImage <image>.
      As a side-effect of the referencing operation, all of the pixel
      data in the <buffer> used as the EGLImage source resource (i.e.,
      the <buffer> parameter passed to the CreateImageKHR command that
      returned <image>) will become undefined.


      The resulting VGImage may be used normally by all OpenVG
      operations, including the creation of child images.  All child
      images of VGImages created using vgCreateEGLImageTargetKHR (and
      their children, etc.) are also EGLImage targets, and will remain
      EGLImage targets until destroyed by subsequent calls to
      vgDestroyImage.

      ERRORS

      VG_UNSUPPORTED_IMAGE_FORMAT_ERROR
      - if the OpenVG implementation is not able to create a VGImage
        compatible with the provided VGeglImageKHR for an implementation-
        dependent reason (this could be caused by, but not limited to,
        reasons such as unsupported pixel formats, anti-aliasing quality,
        etc.).

      VG_ILLEGAL_ARGUMENT_ERROR
      - if <image> is not a valid VGeglImageKHR.

Issues

    1.  Should it be legal behavior to create OpenVG child images from
        parent images which are EGLImage targets?

        RESOLVED:  Yes; this does not add significant implementation
        complexity, so restricting VGImages created using
        CreateEGLImageTargetKHR would be an unnecessary burden on application
        developers.  All child images should also be EGLImage targets. 

    2.  What about portability problems created by allowing
        implementation-dependent failures?

        UNRESOLVED:  See Issue 14 in EGL_KHR_image and issue 4 in
        GL_KHR_EGL_image.

    3.  Should pixel data in image arrays associated with eglImageKHR
        objects used as EGLImage sources in calls to
        CreateEGLImageTargetKHR result in undefined pixel data?

        UNRESOLVED:  See Issue 4 in the GL_KHR_EGL_image specification.

Revision History

#4  (December 14, 2006)

     - Changed requirement to egl 1.2 to include EGLClientBuffer type.

#3   November 27, 2006

     - Changed OES token to KHR

#2   October 20, 2006

     - Rewording phrasing regarding undefined pixel data as a result of
       CreateEGLImageTargetOES

#1    - Original Release