/*

     File: CIExposureView.m

 Abstract: View for drawing and event handling.

  Version: 1.1

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 */

#import "CIExposureView.h"

@interface CIExposureView ()

@property (nonatomic, strong) CIFilter *filter;

@property (assign) float exposureValue;

@end

@implementation CIExposureView

- (void)awakeFromNib 

{

    /*

     Enabling QuartzGL for this window greatly improves rendering preformance when Core Image drawing goes to a Core Graphics context.

     */

    [self.window setPreferredBackingLocation:NSWindowBackingLocationVideoMemory];

}

- (IBAction)sliderChanged:(id)sender

{

    self.exposureValue = [sender floatValue];

    [self setNeedsDisplay: YES];

}

- (void)drawRect:(NSRect)rect

{

    if (self.filter == nil)

    {

        /*

         First time around, we load the image from disk and instantiate the filter object. Holding on to the image and the filter improves performance as it avoids memory allocations and I/O on subsequent draw calls.

        */

        NSURL *imageURL = [[NSBundle mainBundle] URLForResource:@"Rose" withExtension:@"jpg"];

        CIImage *image = [CIImage imageWithContentsOfURL:imageURL];

        self.filter = [CIFilter filterWithName: @"CIExposureAdjust" keysAndValues:@"inputImage", image, nil];

    }

    [self.filter setValue:@(self.exposureValue) forKey:@"inputEV"];

    CIContext *context = [[NSGraphicsContext currentContext] CIContext];

    if (context != nil) {

        CIImage *image = [self.filter valueForKey: @"outputImage"];

        [context drawImage:image inRect:self.bounds fromRect:image.extent];

    }

}

@end