/*

     File: AVSECropCommand.m

 Abstract: A subclass of AVSECommand which uses AVMutableVideoComposition to achieve a crop effect. This tool crops the bottom right quadrant of a composition. This is achieved by reducing the video composition's render size to half of original and then applying a CGAffineTransformMakeTranslation transform to move the appropriate quadrant into view.

  Version: 1.0

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*/

#import "AVSECropCommand.h"

@implementation AVSECropCommand

@synthesize mutableComposition;

@synthesize mutableVideoComposition;

- (void)performWithAsset:(AVAsset*)asset

{

    AVMutableVideoCompositionInstruction *instruction = nil;

    AVMutableVideoCompositionLayerInstruction *layerInstruction = nil;

    CGAffineTransform t1;

    AVAssetTrack *videoTrack = nil;

    AVAssetTrack *audioTrack = nil;

    // Check if the asset contains video and audio tracks

    if ([[asset tracksWithMediaType:AVMediaTypeVideo] count] != 0) {

        videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

    }

    if ([[asset tracksWithMediaType:AVMediaTypeAudio] count] != 0) {

        audioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];

    }

    CMTime insertionPoint = kCMTimeZero;

    NSError * error = nil;

    // Check whether a composition has already been created, i.e, some other tool has already been applied.

    if (!mutableComposition) { 

        // Create a new composition

        mutableComposition = [AVMutableComposition composition];

        // Insert the video and audio tracks from AVAsset 

        if (videoTrack != nil) {

            AVMutableCompositionTrack *vtrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

            [vtrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:videoTrack atTime:insertionPoint error:&error];

        }

        if (audioTrack != nil) {

            AVMutableCompositionTrack *atrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

            [atrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:audioTrack atTime:insertionPoint error:&error];

        }

    }

    // Check whether a video composition already exists to set the appropriate render sizes and transforms

    if (!mutableVideoComposition) {

        // Create a new video composition

        mutableVideoComposition = [AVMutableVideoComposition videoComposition];

        // Render size reduced to half to achieve the crop effect

        mutableVideoComposition.renderSize = CGSizeMake(mutableComposition.naturalSize.width/2, mutableComposition.naturalSize.height/2);

        mutableVideoComposition.frameDuration = CMTimeMake(1, 30);

        // The crop transform is set on a layer instruction  

        instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];

        instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [mutableComposition duration]);

        layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:[mutableComposition.tracks objectAtIndex:0]];

        // Crop transformation (translation to move the bottom right half into the view)

        t1 = CGAffineTransformMakeTranslation(-1*mutableComposition.naturalSize.width/2, -1*mutableComposition.naturalSize.height/2); 

        [layerInstruction setTransform:t1 atTime:kCMTimeZero];

    }else{

        mutableVideoComposition.renderSize = CGSizeMake(mutableVideoComposition.renderSize.width/2, mutableVideoComposition.renderSize.height/2);

        // Extract the existing layer instruction on the mutableVideoComposition

        instruction = [mutableVideoComposition.instructions objectAtIndex:0];

        layerInstruction = [instruction.layerInstructions objectAtIndex:0];

        // Check if a transform already exists on this layer instruction, this is done to add the current transform on top of previous edits

        CGAffineTransform existingTransform;

        if (![layerInstruction getTransformRampForTime:[mutableComposition duration] startTransform:&existingTransform endTransform:NULL timeRange:NULL]) {

            t1 = CGAffineTransformMakeTranslation(-1*mutableComposition.naturalSize.width/2, -1*mutableComposition.naturalSize.height/2); 

            [layerInstruction setTransform:t1 atTime:kCMTimeZero];

        }else {

            t1 = CGAffineTransformMakeTranslation(-1*mutableVideoComposition.renderSize.width, -1*mutableVideoComposition.renderSize.height); 

            CGAffineTransform newTransform = CGAffineTransformConcat(existingTransform, t1);

            [layerInstruction setTransform:newTransform atTime:kCMTimeZero];

        }

    }

     // Add the layer instruction to an instruction which is then added to the mutableVideoComposition

    instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];

    mutableVideoComposition.instructions = [NSArray arrayWithObject: instruction];

    // Notify AVSEDocument class to reload the player view with the changes

    [[NSNotificationCenter defaultCenter] 

     postNotificationName:AVSEReloadNotification 

     object:self];

}

@end