快捷導(dǎo)航

iOS開(kāi)發(fā)中實(shí)現(xiàn)顯示gif圖片的方法

更新時(shí)間：2015年09月26日 10:02:24 作者：一片楓葉

這篇文章主要介紹了iOS開(kāi)發(fā)中實(shí)現(xiàn)顯示gif圖片的方法,代碼基于傳統(tǒng)的Objective-C,需要的朋友可以參考下

我們知道Gif是由一陣陣畫面組成的，而且每一幀畫面播放的時(shí)常可能會(huì)不相等，觀察上面兩個(gè)例子，發(fā)現(xiàn)他們都沒(méi)有對(duì)Gif中每一幀的顯示時(shí)常做處理，這樣的結(jié)果就是整個(gè)Gif中每一幀畫面都是以固定的速度向前播放，很顯然這并不總會(huì)符合需求。

　　于是自己寫一個(gè)解析Gif的工具類，解決每一幀畫面并遵循每一幀所對(duì)應(yīng)的顯示時(shí)間進(jìn)行播放。

　　程序的思路如下：

　　1、首先使用ImageIO庫(kù)中的CGImageSource家在Gif文件。

　　2、通過(guò)CGImageSource獲取到Gif文件中的總的幀數(shù)，以及每一幀的顯示時(shí)間。

　　3、通過(guò)CAKeyframeAnimation來(lái)完成Gif動(dòng)畫的播放。

　　下面直接上我寫的解析和播放Gif的工具類的代碼：

復(fù)制代碼代碼如下:

//
// SvGifView.h
// SvGifSample
//
// Created by maple on 3/28/13.
// Copyright (c) 2013 smileEvday. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface SvGifView : UIView

/*
* @brief desingated initializer
*/
- (id)initWithCenter:(CGPoint)center fileURL:(NSURL*)fileURL;

/*
* @brief start Gif Animation
*/
- (void)startGif;

/*
* @brief stop Gif Animation
*/
- (void)stopGif;

/*
* @brief get frames image(CGImageRef) in Gif
*/
+ (NSArray*)framesInGif:(NSURL*)fileURL;

@end

//
// SvGifView.m
// SvGifSample
//
// Created by maple on 3/28/13.
// Copyright (c) 2013 smileEvday. All rights reserved.
//

#import "SvGifView.h"
#import <ImageIO/ImageIO.h>
#import <QuartzCore/CoreAnimation.h>

/*
* @brief resolving gif information
*/
void getFrameInfo(CFURLRef url, NSMutableArray *frames, NSMutableArray *delayTimes, CGFloat *totalTime,CGFloat *gifWidth, CGFloat *gifHeight)
{
    CGImageSourceRef gifSource = CGImageSourceCreateWithURL(url, NULL);

    // get frame count
    size_t frameCount = CGImageSourceGetCount(gifSource);
    for (size_t i = 0; i < frameCount; ++i) {
        // get each frame
        CGImageRef frame = CGImageSourceCreateImageAtIndex(gifSource, i, NULL);
        [frames addObject:(id)frame];
        CGImageRelease(frame);

        // get gif info with each frame
        NSDictionary *dict = (NSDictionary*)CGImageSourceCopyPropertiesAtIndex(gifSource, i, NULL);
        NSLog(@"kCGImagePropertyGIFDictionary %@", [dict valueForKey:(NSString*)kCGImagePropertyGIFDictionary]);

        // get gif size
        if (gifWidth != NULL && gifHeight != NULL) {
            *gifWidth = [[dict valueForKey:(NSString*)kCGImagePropertyPixelWidth] floatValue];
            *gifHeight = [[dict valueForKey:(NSString*)kCGImagePropertyPixelHeight] floatValue];
        }

        // kCGImagePropertyGIFDictionary中kCGImagePropertyGIFDelayTime，kCGImagePropertyGIFUnclampedDelayTime值是一樣的
        NSDictionary *gifDict = [dict valueForKey:(NSString*)kCGImagePropertyGIFDictionary];
        [delayTimes addObject:[gifDict valueForKey:(NSString*)kCGImagePropertyGIFDelayTime]];

        if (totalTime) {
            *totalTime = *totalTime + [[gifDict valueForKey:(NSString*)kCGImagePropertyGIFDelayTime] floatValue];
        }
    }
}

@interface SvGifView() {
    NSMutableArray *_frames;
    NSMutableArray *_frameDelayTimes;

    CGFloat _totalTime;         // seconds
    CGFloat _width;
    CGFloat _height;
}

@end

@implementation SvGifView

- (id)initWithCenter:(CGPoint)center fileURL:(NSURL*)fileURL;
{
    self = [super initWithFrame:CGRectZero];
    if (self) {

        _frames = [[NSMutableArray alloc] init];
        _frameDelayTimes = [[NSMutableArray alloc] init];

        _width = 0;
        _height = 0;

        if (fileURL) {
            getFrameInfo((CFURLRef)fileURL, _frames, _frameDelayTimes, &_totalTime, &_width, &_height);
        }

        self.frame = CGRectMake(0, 0, _width, _height);
        self.center = center;
    }

    return self;
}

+ (NSArray*)framesInGif:(NSURL *)fileURL
{
    NSMutableArray *frames = [NSMutableArray arrayWithCapacity:3];
    NSMutableArray *delays = [NSMutableArray arrayWithCapacity:3];

    getFrameInfo((CFURLRef)fileURL, frames, delays, NULL, NULL, NULL);

    return frames;
}

- (void)startGif
{
    CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"contents"];

    NSMutableArray *times = [NSMutableArray arrayWithCapacity:3];
    CGFloat currentTime = 0;
    int count = _frameDelayTimes.count;
    for (int i = 0; i < count; ++i) {
        [times addObject:[NSNumber numberWithFloat:(currentTime / _totalTime)]];
        currentTime += [[_frameDelayTimes objectAtIndex:i] floatValue];
    }
    [animation setKeyTimes:times];

    NSMutableArray *images = [NSMutableArray arrayWithCapacity:3];
    for (int i = 0; i < count; ++i) {
        [images addObject:[_frames objectAtIndex:i]];
    }

    [animation setValues:images];
    [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];
    animation.duration = _totalTime;
    animation.delegate = self;
    animation.repeatCount = 5;

    [self.layer addAnimation:animation forKey:@"gifAnimation"];
}

- (void)stopGif
{
[self.layer removeAllAnimations];
}

// remove contents when animation end
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
self.layer.contents = nil;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
// Drawing code
}

@end

　　代碼很短也比較容易，就不一一解釋了。最開(kāi)始的那個(gè)C函數(shù)主要就是用來(lái)解析Gif的，之所以用C函數(shù)是因?yàn)槲乙祷囟鄠€(gè)信息，而Objective-c只能返回一個(gè)參數(shù)，而且Objective-c和C語(yǔ)言可以很方便的混合編程。

另外再介紹兩種使用UIImageView的方法：

1. 使用UIWebView播放

復(fù)制代碼代碼如下:

    // 設(shè)定位置和大小

    CGRect frame = CGRectMake(50,50,0,0);

    frame.size = [UIImage imageNamed:@"guzhang.gif"].size;

    // 讀取gif圖片數(shù)據(jù)

    NSData *gif = [NSData dataWithContentsOfFile: [[NSBundle mainBundle] pathForResource:@"guzhang" ofType:@"gif"]];

    // view生成

    UIWebView *webView = [[UIWebView alloc] initWithFrame:frame];

    webView.userInteractionEnabled = NO;//用戶不可交互

    [webView loadData:gif MIMEType:@"image/gif" textEncodingName:nil baseURL:nil];

    [self.view addSubview:webView];

    [webView release];

2.將gif圖片分解成多張png圖片，使用UIImageView播放。
代碼如下：

復(fù)制代碼代碼如下:

 UIImageView *gifImageView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    NSArray *gifArray = [NSArray arrayWithObjects:[UIImage imageNamed:@"1"],

                                                  [UIImage imageNamed:@"2"],

                                                  [UIImage imageNamed:@"3"],

                                                  [UIImage imageNamed:@"4"],

                                                  [UIImage imageNamed:@"5"],

                                                  [UIImage imageNamed:@"6"],

                                                  [UIImage imageNamed:@"7"],

                                                  [UIImage imageNamed:@"8"],

                                                  [UIImage imageNamed:@"9"],

                                                  [UIImage imageNamed:@"10"],

                                                  [UIImage imageNamed:@"11"],

                                                  [UIImage imageNamed:@"12"],

                                                  [UIImage imageNamed:@"13"],

                                                  [UIImage imageNamed:@"14"],

                                                  [UIImage imageNamed:@"15"],

                                                  [UIImage imageNamed:@"16"],

                                                  [UIImage imageNamed:@"17"],

                                                  [UIImage imageNamed:@"18"],

                                                  [UIImage imageNamed:@"19"],

                                                  [UIImage imageNamed:@"20"],

                                                  [UIImage imageNamed:@"21"],

                                                  [UIImage imageNamed:@"22"],nil];

    gifImageView.animationImages = gifArray; //動(dòng)畫圖片數(shù)組

    gifImageView.animationDuration = 5; //執(zhí)行一次完整動(dòng)畫所需的時(shí)長(zhǎng)

    gifImageView.animationRepeatCount = 1;  //動(dòng)畫重復(fù)次數(shù)

    [gifImageView startAnimating];

    [self.view addSubview:gifImageView];

    [gifImageView release];