The Is Identity Action

The Is Identity Action
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	#include "ofxImageEffect.h"
	#define kOfxImageEffectActionIsIdentity            "OfxImageEffectActionIsIdentity"

Arguments

handle handle to the instance, cast to an OfxImageEffectHandle ,
inArgs has the following properties...
- kOfxPropTime - the time at which to test for identity
- kOfxImageEffectPropFieldToRender - the field to test for identity
- kOfxImageEffectPropRenderWindow - the window (in \ref PixelCoordinates) to test for identity under
- kOfxImageEffectPropRenderScale - the scale factor being applied to the images being renderred
outArgs has the following properties which the plugin can set...
- kOfxPropName this to the name of the clip that should be used if the effect is an identity transform, defaults to the empty string
- kOfxPropTime the time to use from the indicated source clip as an identity image (allowing time slips to happen), defaults to the value in kOfxPropTime in inArgs

Description

Sometimes an effect can pass through an input uprocessed, for example a blur effect with a blur size of 0. This action can be called by a host before it attempts to render an effect to determine if it can simply copy input directly to output without having to call the render action on the effect.

If the effect does not need to process any pixels, it should set the value of the kOfxPropName to the clip that the host should us as the output instead, and the kOfxPropTime property on outArgs to be the time at which the frame should be fetched from a clip.

Return Values

kOfxStatOK, the action was trapped and the effect should not have its render action called, the values in outArgs indicate what frame from which clip to use instead
kOfxStatReplyDefault, the action was not trapped and the host should call the render action
kOfxStatErrMemory, in which case the action may be called again after a memory purge
kOfxStatFailed, something wrong, but no error code appropriate, plugin to post message
kOfxStatErrFatal

Default Action

The default action is to call the render action on the effect.

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