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Host Origin Hints Proposed

Standard version: 1.4

Minor Change

RE:Vision Effects needs that. This was reviewed with TuttleOFX last year in the generic mailing list.

renamed for consistency:

kOfxImageEffectHostPropNativeOrigin

 

Sometimes it is good for a plugin to know where the native origin of the host is and whether the coordinate system is Y-Up or Y-Down. This is strictly a UI hint to plugin.

It's good we have a simple base image / frame buffer model (lower-left, RGBA, rowbytes...) - however some applications are natively not lower-left which makes integration of the plugin complicated - for example point parameters (and overlay drawing) if they can be connected to a tracker from the host are suddenly upside down of where they should be. 

All this hint does is tell plugin that the host world is different than OFX. Historically the first two hosts that exhibited this issue could be Fusion (upper left is 0,0 natively) and Toxic (Center is 0,0).  

Add in a property to the host's property set, one that describe the location of the origin.

  • kOfxImageEffectHostPropNativeOrigin - a 1D string prop that can be one of 
    • kOfxHostNativeOriginBottomLeft   // default - same as before
    • kOfxHostNativeOriginTopLeft 
    • kOfxHostNativeOriginCentre 

 

 This has no effect on image data, an host can pass negative rowbytes to avoid flipping the image to pass to OFX plugins.

 

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Discussion

Comments

The second item is related to image scanline order. This in theory is defined by the sign of rowbytes. 

So I removed:

  • kOfxHostPropNativeYDirection - a 1D string prop that can be one of 
    • kOfxHostNativeYDirectionUp
    • kOfxHostNativeYDirectionDown
Pierre Jasmin | 12:00 pm, 19 Jul 2015

Actually this is redundant I think, and perhaps something lost in transcription from original notes. I think we only need kOfxHostPropNativeOrigin. The purpose here is when drawing and locating points that we are putting X,Y in native UI coordinates - so all this makes sense for expressions etc.

The second item is related to image scanline order. This in theory is defined by the sign of rowbytes. 

Pierre Jasmin | 5:08 pm, 13 Jun 2015
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