UIImage+animatedGIF.m 4.42 KB
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#import "UIImage+animatedGIF.h"
#import <ImageIO/ImageIO.h>

#if __has_feature(objc_arc)
#define toCF (__bridge CFTypeRef)
#define fromCF (__bridge id)
#else
#define toCF (CFTypeRef)
#define fromCF (id)
#endif

@implementation UIImage (animatedGIF)

static int delayCentisecondsForImageAtIndex(CGImageSourceRef const source, size_t const i) {
int delayCentiseconds = 1;
CFDictionaryRef const properties = CGImageSourceCopyPropertiesAtIndex(source, i, NULL);
if (properties) {
CFDictionaryRef const gifProperties = CFDictionaryGetValue(properties, kCGImagePropertyGIFDictionary);
if (gifProperties) {
NSNumber *number = fromCF CFDictionaryGetValue(gifProperties, kCGImagePropertyGIFUnclampedDelayTime);
if (number == NULL || [number doubleValue] == 0) {
number = fromCF CFDictionaryGetValue(gifProperties, kCGImagePropertyGIFDelayTime);
}
if ([number doubleValue] > 0) {
// Even though the GIF stores the delay as an integer number of centiseconds, ImageIO “helpfully” converts that to seconds for us.
delayCentiseconds = (int)lrint([number doubleValue] * 100);
}
}
CFRelease(properties);
}
return delayCentiseconds;
}

static void createImagesAndDelays(CGImageSourceRef source, size_t count, CGImageRef imagesOut[count], int delayCentisecondsOut[count]) {
for (size_t i = 0; i < count; ++i) {
imagesOut[i] = CGImageSourceCreateImageAtIndex(source, i, NULL);
delayCentisecondsOut[i] = delayCentisecondsForImageAtIndex(source, i);
}
}

static int sum(size_t const count, int const *const values) {
int theSum = 0;
for (size_t i = 0; i < count; ++i) {
theSum += values[i];
}
return theSum;
}

static int pairGCD(int a, int b) {
if (a < b)
return pairGCD(b, a);
while (true) {
int const r = a % b;
if (r == 0)
return b;
a = b;
b = r;
}
}

static int vectorGCD(size_t const count, int const *const values) {
int gcd = values[0];
for (size_t i = 1; i < count; ++i) {
// Note that after I process the first few elements of the vector, `gcd` will probably be smaller than any remaining element. By passing the smaller value as the second argument to `pairGCD`, I avoid making it swap the arguments.
gcd = pairGCD(values[i], gcd);
}
return gcd;
}

static NSArray *frameArray(size_t const count, CGImageRef const images[count], int const delayCentiseconds[count], int const totalDurationCentiseconds) {
int const gcd = vectorGCD(count, delayCentiseconds);
size_t const frameCount = totalDurationCentiseconds / gcd;
UIImage *frames[frameCount];
for (size_t i = 0, f = 0; i < count; ++i) {
UIImage *const frame = [UIImage imageWithCGImage:images[i]];
for (size_t j = delayCentiseconds[i] / gcd; j > 0; --j) {
frames[f++] = frame;
}
}
return [NSArray arrayWithObjects:frames count:frameCount];
}

static void releaseImages(size_t const count, CGImageRef const images[count]) {
for (size_t i = 0; i < count; ++i) {
CGImageRelease(images[i]);
}
}

static UIImage *animatedImageWithAnimatedGIFImageSource(CGImageSourceRef const source) {
size_t const count = CGImageSourceGetCount(source);
CGImageRef images[count];
int delayCentiseconds[count]; // in centiseconds
createImagesAndDelays(source, count, images, delayCentiseconds);
int const totalDurationCentiseconds = sum(count, delayCentiseconds);
NSArray *const frames = frameArray(count, images, delayCentiseconds, totalDurationCentiseconds);
UIImage *const animation = [UIImage animatedImageWithImages:frames duration:(NSTimeInterval)totalDurationCentiseconds / 100.0];
releaseImages(count, images);
return animation;
}

static UIImage *animatedImageWithAnimatedGIFReleasingImageSource(CGImageSourceRef CF_RELEASES_ARGUMENT source) {
if (source) {
UIImage *const image = animatedImageWithAnimatedGIFImageSource(source);
CFRelease(source);
return image;
} else {
return nil;
}
}

+ (UIImage *)animatedImageWithAnimatedGIFData:(NSData *)data {
return animatedImageWithAnimatedGIFReleasingImageSource(CGImageSourceCreateWithData(toCF data, NULL));
}

+ (UIImage *)animatedImageWithAnimatedGIFURL:(NSURL *)url {
return animatedImageWithAnimatedGIFReleasingImageSource(CGImageSourceCreateWithURL(toCF url, NULL));
}

@end