1.算法程序

  AfterEffect(AE)插件是Adobe公司开发的特效制作软件，稳定快速的功能和特效，在视频制作领域使用非常广泛，本文向大家介绍如何在项目里进行改变层上帧的属性功能。源代码如下所示：

{
    // Convert Selected Properties to Markers.jsx
    // 
    // For each layer that contains selected properties, convert the value of the property at each
    // frame time to an event cue point.
    
    function ConvertSelectedPropertiesToMarkers()
    {
        var scriptName = "Convert Selected Properties to Markers";
        var propsSkipped = new Array();
        
        
        function ConvertPropertyToMarkers(markerStream, prop)
        {
            // Only do properties, not property groups.
            if (!(prop instanceof Property)) {
                return;
            }
        
            // Custom/No_Value property types are not supported, so skip gracefully (but log so we can display useful error message later).
            if ((prop.propertyValueType == PropertyValueType.CUSTOM_VALUE) || (prop.propertyValueType == PropertyValueType.NO_VALUE)) {
                // Log just the first 10 custom properties, as we don't want to display too big of an error message dialog to the user,
                if (propsSkipped.length <= 10) {
                    propsSkipped[propsSkipped.length] = prop.parentProperty.name + " > " + prop.name;
                }
                return;
            }
            
            
            function GenerateIDPathForProp(prop)
            {
                return prop.parentProperty.name + "_" + prop.name;
            }
            
            
            function PrintPropToParmsAtTime(parms, prop, time)
            {
                parms[GenerateIDPathForProp(prop)] = prop.valueAtTime(time, false);
            }
            
            
            function SampleAtTime(markerStream, prop, time)
            {
                var existingMarker = markerStream.valueAtTime(time, false);
                var curParms = existingMarker.getParameters();
                PrintPropToParmsAtTime(curParms, prop, time);
                existingMarker.setParameters(curParms);
                existingMarker.cuePointName = time;         // added in 9.0.1 update
                markerStream.setValueAtTime(time, existingMarker);      
            }
            
            
            // Sample the whole property,
            var owningLayer = prop;
            for (var depth = prop.propertyDepth; depth > 0; --depth) {
                owningLayer = owningLayer.parentProperty;
            }
            if (prop.expressionEnabled) {
                // For properties with enabled expressions, add markers at each frame between the In and Out points.
                var curTime = owningLayer.inPoint;
                var outTime = owningLayer.outPoint;
                for ( ; curTime <= outTime; curTime += owningLayer.containingComp.frameDuration) {
                    SampleAtTime(markerStream, prop, curTime);
                }
            } else {
                // Look just between the first and last keyframes.
                if (prop.numKeys) {
                    for (var i = 1; i <= prop.numKeys; ++i) {
                        var keyTime = prop.keyTime(i);
                        SampleAtTime(markerStream, prop, keyTime);
                    }
                } else {
                    SampleAtTime(markerStream, prop, owningLayer.startTime);
                }
            }
        }
        
        if (app.project && app.project.activeItem && app.project.activeItem instanceof CompItem) {
            // Process the active composition's layers that have selected properties.
            app.beginUndoGroup(scriptName);
            var layerColl = app.project.activeItem.layers;
            for (var i = 1; i <= layerColl.length; ++i) {
                var curLayer = layerColl[i];
                if (curLayer.selectedProperties && curLayer.selectedProperties.length > 0) {
                    var selProps = curLayer.selectedProperties;
                    for (var propIdx = 0; propIdx < selProps.length; ++propIdx ) {
                        ConvertPropertyToMarkers(curLayer.marker, selProps[propIdx]);
                    }
                }
            }
            app.endUndoGroup();
            
            // Display any errors to the user (show only the first 10).
            if (propsSkipped.length > 0) {
                var errorStr = "Custom properties and properties with no value are not supported at this time, and did not get converted.\r\rSelected properties skipped include:\r";
                for (var i=0; i<propsSkipped.length; i++) {
                    errorStr += propsSkipped[i] + "\r";
                }
                alert(errorStr, scriptName);
            }
        }
    }
    
    
    ConvertSelectedPropertiesToMarkers();
}

2.作者答疑

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