#2: unified pix-orientation

Contents

1. Motivation
2. Assumptions
3. Proposal
4. Risks

Proposed by

IOhannes m zmölnig

Proposal type

Architecture

State

being-discussed

Motivation

pixes of different orientation (upsidedown=false, upsidedown=true) make more problems then they solve

• mixing pixes gives weird results
• texture-coordinates handling becomes complicated
  • e.g. uv-texturing of ![model]

Assumptions

definitions

• "upsidedown" means that the pix is delivered with top-down orientation and the "upsidedown" flag is set
• "manually flipped" means, that the pixes are acquired with top-down but are then flipped using CPU-cycles and delivered as bottom-down
• "row indices" indicates that the pix is acquired bottom-up by copying the image line-by-line; thus performance should be the same whether the image is delivered bottom-up and top-down
• "unflipped" delivers pixes bottom-up which is how the pixes are natively acquired

current state:

image-sources:

• magickImage2mem:

  manually flipped from top-down to bottom-up

• tiffImage2mem

  manually flipped from top-down to bottom-up

• jpegImage2mem

  manually flipping the image(?)

• sgiImage2mem (iris image format)

  unflipped(?)

• QtImage2mem (OSX)
• filmQT

  upsidedown

• filmDarwin (OSX)
• filmQT4L

  row-indices

• filmMPEG3

  RGBA: row-indices

  YUV: upsidedown

• filmMPEG1

  upsidedown

• filmGMERLIN

  upsidedown

• filmFFMPEG

  upsidedown

• filmDS (DirectShow)

  unflipped(?)

• filmAVIPLAY

  upsidedown

• filmAVI (VfW)

  unflipped (manually?)

• videoDV4L

  upsidedown

• videoV4L

  upsidedown

• videoV4L2

  upsidedown

backend-specific objects

• pix_filmQT

  upsidedown

• pix_videoSGI

  manually flipped

• pix_filmDarwin (OSX)
• pix_filmNT (VfW)
• pix_videoDS (DirectShow)
• pix_videoNT (VfW)
• pix_videoDarwin (OSX)

OS specifics

• OSX:

  everything is upsidedown

• w32:
  • see http://www.microsoft.com/whdc/archive/biheight.mspx
  • VfW
    • RGBA bottom-up
    • YUV top-down
  • DirectDraw: top-down
  • DirectShow: both?

Proposal

all pixes should be of the same orientation

i propose that this orientation should be top-down (as opposed to the openGL-default bottom-up), since most video-codecs will deliver the images top-down anyhow

for static images the penalty of flipping the images should be minimal

Risks

the only problem is see is with generated images (using [pix_snap], [pix_snap2tex], [gemframebuffer]), as these will have the default openGL orientation (thus re-introducing the wrong orientation)