UIImage有关的几个方法

1） UIImage类imageNamed方法是便捷的便捷构造方法， 使用了自动释放池， 在需要频繁大量加载图片的场合请不要使用imageNamed, 而
imageWithContentsOfFile， 


2） 如何将解码后的RGB24数据显示到UIImage上
#define SCREEN_METRIC_WIDTH 176
#define SCREEN_METRIC_HEIGHT 144
int i = 0;    
    
int bitsPerComponent = 8;    
int bitsPerPixel = 24;    
int bytesPerRow = 3 * SCREEN_METRIC_WIDTH;    
NSInteger myLCDDataLength =     
SCREEN_METRIC_WIDTH * SCREEN_METRIC_HEIGHT * 3;    
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();    
CGBitmapInfo bmpInof = kCGBitmapByteOrderDefault;    
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;    
CGDataProviderRef provider = nil;  
    
//rgb_image = malloc(SCREEN_METRIC_WIDTH*SCREEN_METRIC_HEIGHT*3)


provider = CGDataProviderCreateWithData(NULL, rgb_image, myLCDDataLength, NULL);    
    
CGImageRef cgImage=  CGImageCreate(SCREEN_METRIC_WIDTH,SCREEN_METRIC_HEIGHT,    
                         bitsPerComponent,    
                         bitsPerPixel,    
                         bytesPerRow,    
                         colorSpaceRef,    
                         bmpInof,    
                         provider,    
                         NULL,     
                         NO,    
                         renderingIntent);    
    
CGColorSpaceRelease(colorSpaceRef);
UIImage *image = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);
CGDataProviderRelease(provider);


3） 把UIImage数据保存文件


    //get now time
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyy_MMdd_HHMMSS"];
    NSString *dateTime = [formatter stringFromDate:[NSDate date]];
    
    NSString* filepath = [Utilities documentsPath:[NSString stringWithFormat:@"snapshot%@.png", dateTime]];
    
    NSLog(@"save png, time:%@", filepath);
    
    [formatter release];   
    
    //save UIImage to file in PNG format
    NSData *imageData = NULL;
    
    imageData = UIImagePNGRepresentation(cur_uiImage);
    if ((imageData == nil) || ([imageData length] <= 0))
        return 0;
    
    [imageData writeToFile:filepath atomically:YES];  
    //直接保存图片到相册
    //UIImageWriteToSavedPhotosAlbum(cur_uiImage, nil, nil, nil);








4） 截取整个UIView并保存文件
 
UIView *view = [[[[[UIApplication sharedApplication] windows] objectAtIndex:1] subviews] lastObject];//获得某个window的某个subView
 
NSInteger index = 0;//用来给保存的png命名
for (UIView *subView in [view subviews]) {//遍历这个view的subViews
    if ([subView isKindOfClass:NSClassFromString(@"UIImageView")] || [subView isKindOfClass:NSClassFromString(@"UIThreePartButton")]) {//找到自己需要的subView
        //支持retina高分的关键
        if(UIGraphicsBeginImageContextWithOpti***** != NULL)
        {
            UIGraphicsBeginImageContextWithOpti*****(subView.frame.size, NO, 0.0);
        } else {
            UIGraphicsBeginImageContext(subView.frame.size);
        }            
         
        //获取图像
        [subView.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
         
        //保存图像
        NSString *path = [NSHomeDirectory() stringByAppendingFormat:@"/%d.png",index];
        if ([UIImagePNGRepresentation(image) writeToFile:path atomically:YES]) {
            index += 1;
            NSLog(@"Succeeded!");
        }
        else {
            NSLog(@"Failed!");
        }
    }
}