一些有关图像处理的代码片段(抓图、倒影、圆角)

 

捕捉屏幕截图
CALayer实例使用Core Graphics的renderInContext方法可以将视图绘制到图像上下文中以便转化为其他UIImage实例。前提先#import <QuartzCore/QuartzCore.h>

+ (UIImage *) imageFromView: (UIView *)theView {
//
 draw a view's contents into an image context


   UIGraphicsBeginImageContext(theView.frame.size);

   CGContextRef  context = UIGraphicsGetCurrentContext();


   [theView.layer  renderInContext:context];

   UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();

   UIGraphicsEndImageContext(); 
return
 theImage;

}

注：UIGraphicsBeginImageContext(CGSize size)创建一个基于位图的上下文(context)，并将其设置为当前上下文。函数功能与UIGraphicsBeginImageContextWithOptions相同，相当于该方法的opaque参数为NO，scale因子为1.0。而UIGraphicsEndImageContext()方法是移除栈顶的基于当前位图的图形上下文。

捕捉截取某个区域内屏幕图像

- (UIImage *)imageFromView: (UIView *) theView  atFrame:(CGRect)rect

{

    UIGraphicsBeginImageContext(theView.frame.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSaveGState(context);

    UIRectClip(rect);

    [theView.layer renderInContext:context];

    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

return
  theImage;//
[self getImageAreaFromImage:theImage atFrame:rect];


}

从某图片中截图

UIImage *image = [[UIImage alloc] initWithData:data];//
大图


CGRect imageRect = CGRectMake(0.0
, 0.0
, image.size.width, image.size.height);

CGSize itemSize = CGSizeMake(w,h);

UIGraphicsBeginImageContext(itemSize);

[image drawInRect:imageRect];

UIImage *smallimage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext(); 

视图添加倒影效果

const
 CGFloat kReflectPercent = -0.25f
;
const
 CGFloat kReflectOpacity = 0.3f
;
const
 CGFloat kReflectDistance = 10.0f
;


+ (void
)addSimpleReflectionToView:(UIView *)theView

{

     CALayer *reflectionLayer = [CALayer layer];

     reflectionLayer.contents = [theView layer].contents;

     reflectionLayer.opacity = kReflectOpacity;

     reflectionLayer.frame = CGRectMake(0.0f
,0.0f
,theView.frame.size.width,theView.frame.size.height*kReflectPercent);  //
倒影层框架设置，其中高度是原视图的百分比


    CATransform3D stransform = CATransform3DMakeScale(1.0f
,-1.0f
,1.0f
);

     CATransform3D transform = CATransform3DTranslate(stransform,0.0f
,-(kReflectDistance + theView.frame.size.height),0.0f
);

     reflectionLayer.transform = transform;

     reflectionLayer.sublayerTransform = reflectionLayer.transform;

     [[theView layer] addSublayer:reflectionLayer];

}

 另一：使用Core Graphics创建倒影

+ (CGImageRef) createGradientImage:(CGSize)size

{

      CGFloat colors[] = {0.0
,1.0
,1.0
,1.0
};
//
在灰色设备色彩上建立一渐变


     CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

      CGContextRef context = CGBitmapContextCreate(nil,size.width,size.height,8
,0
,colorSpace,kCGImageAlphaNone);

      CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace,colors,NULL,2
);

      CGColorSpaceRelease(colorSpace);

//
绘制线性渐变


     CGPoint p1 = CGPointZero;

      CGPoint p2 = CGPointMake(0
,size.height);

      CGContextDrawLinearGradient(context,gradient,p1,p2,kCGGradientDrawsAfterEndLocation);

//
Return the CGImage


      CGImageRef theCGImage = CGBitmapContextCreateImage(context);

      CFRelease(gradient);

      CGContextRelease(context);
return
 theCGImage;

}

//Create a shrunken frame for the reflection

+ (UIImage *) reflectionOfView:(UIView *)theView WithPercent:(CGFloat) percent

{
//
Retain the width but shrink the height


     CGSize size = CGSizeMake(theView.frame.size.width, theView.frame.size.height * percent);

//
Shrink the View


     UIGraphicsBeginImageContext(size);

     CGContextRef context = UIGraphicsGetCurrentContext();

     [theView.layer renderInContext:context];

     UIImage *partialimg = UIGraphicsGetImageFromCurrentImageContext();

     UIGraphicsEndImageContext();

//
build the mask


     CGImageRef mask = [ImageHelper createGradientImage:size];

     CGImageRef ref
 = CGImageCreateWithMask(partialimg.CGImage,mask);

     UIImage *theImage = [UIImage imageWithCGImage:ref
];

     CGImageRelease(ref
);

     CGImageRelease(mask);
return
 theImage;

}

const
 CGFloat kReflectDistance = 10.0f
;

+ (void
) addReflectionToView: (UIView *)theView

{

     theView.clipsToBounds = NO;

     UIImageView *reflection = [[UIImageView alloc] initWithImage:[ImageHelper reflectionOfView:theView withPercent:0.45f
]];

     CGRect frame = reflection.frame;

     frame.origin = CGPointMake(0.0f
, theView.frame.size.height + kReflectDistance);

     reflection.frame = frame;

//
 add the reflection as a simple subview


     [theView addSubView:reflection];

     [reflection release];

}

实现圆角图片：

UIColor *color = [UIColor colorWithRed:0.95
 green:0.95
 blue:0.95
 alpha:0
];

[aImage setBackgroundColor:color]; //
设置背景透明



/*
*****设置图片圆角begin******
*/


aImage.layer.masksToBounds = YES;

aImage.layer.cornerRadius = 5.0
;

aImage.layer.borderWidth = 0.5
;

aImage.layer.borderColor = [[UIColor grayColor] CGColor];
/*
*****设置图片圆角end*******
*/

另有方法可见：http://www.4ucode.com/Study/Topic/2058289转载文章。

实现iPhone图标的水晶立体效果

- (void
)viewDidLoad {

    [super viewDidLoad];

    UIGraphicsBeginImageContext(icon.bounds.size);

    CGContextRef ctx = UIGraphicsGetCurrentContext();
const
 CGFloat components[4
] = {0.0
,0.4
,0.0
,1.0
};

    CGContextSetFillColor(ctx, components);

    CGContextFillRect(ctx, CGRectMake(0
, 0
, icon.bounds.size.width, icon.bounds.size.height));

    UIImage *background = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    UIImage *image = [UIImage imageNamed:@"
icon.png
"
];

    UIImage *mask = [UIImage imageNamed:@"
IconBase.png
"
];

    UIImage *roundCorner = [UIImage imageNamed:@"
round-corner.png
"
];

    icon.image = image;

    CALayer* subLayer = [[CALayer layer] retain];

    subLayer.frame = icon.bounds;

    subLayer.contents = (id
)[background CGImage];

    CALayer* maskLayer = [[CALayer layer] retain];

    maskLayer.frame = icon.bounds;

    maskLayer.contents = (id
)[mask CGImage]; 

    [subLayer setMask:maskLayer];

    [[icon layer] addSublayer:subLayer];

    CALayer* roundCornerLayer = [[CALayer layer] retain];

    roundCornerLayer.frame = icon.bounds;

    roundCornerLayer.contents = (id
)[roundCorner CGImage];

    [[icon layer] setMask:roundCornerLayer];

    [maskLayer release];

    [subLayer release];

    [roundCornerLayer release];

}

两图合成一图

- (UIImage*)addImage:(UIImage *)image1 toImage:(UIImage*)image2

{

    UIGraphicsBeginImageContext(image1.size);


    [image1 drawInRect:CGRectMake(0
,0
,image1.size.width,image1.size.height)];

    [image2 drawInRect:CGRectMake(0
,0
,image2.size.width,image2.size.height)];


    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
return
 resultingImage;

}