UIGraphicsBeginImageCont
创建一个基于位图的上下文（context）,并将其设置为当前上下文(context)。方法声明如下：
参数size为新创建的位图上下文的大小。它同时是由UIGraphicsGetImageFromCu
该函数的功能同UIGraphicsBeginImageCont
UIGraphicsBeginImageCont
函数原型为：
size——同UIGraphicsBeginImageCont
opaque—透明开关，如果图形完全不用透明，设置为YES以优化位图的存储。
scale—–缩放因子
UIImageC处理
1、等比缩放
- - (UIImage *) scaleImage:(UIImage *)image toScale:(float)scaleSize {
- UIGraphicsBeginImageCont
ext(CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize); - [image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height * scaleSize)];
- UIImage *scaledImage = UIGraphicsGetImageFromCu
rrentImageContext(); - UIGraphicsEndImageContex
t(); - return scaledImage;
- }
2、自定义大小
- - (UIImage *) reSizeImage:(UIImage *)image toSize:(CGSize)reSize {
- UIGraphicsBeginImageCont
ext(CGSizeMake(reSize.width, reSize.height)); - [image drawInRect:CGRectMake(0, 0, reSize.width, reSize.height)];
- UIImage *reSizeImage = UIGraphicsGetImageFromCu
rrentImageContext(); - UIGraphicsEndImageContex
t(); - return reSizeImage;
- }
3、处理某个特定的view
只要是继承UIView的object 都可以处理
必须先import QuzrtzCore.framework
- -(UIImage*) captureView:(UIView *)theView {
- CGRect rect = theView.frame;
- UIGraphicsBeginImageCont
ext(rect.size); - CGContextRef context = UIGraphicsGetCurrentCont
ext(); - [theView.layer renderInContext:context];
- UIImage *img = UIGraphicsGetImageFromCu
rrentImageContext(); - UIGraphicsEndImageContex
t(); - return img;
- }
4、存储图片
4.1、存储到app的文件里
把要处理的图片以image.png的名字存储到app home地下的Document目录中
- NSString *path = [[NSHomeDirectory()stringByAppendingPathCom
ponent:@ "Documents"]stringByAppendingPathComponent:@ "image.png"]; - [UIImagePNGRepresentation
(image) writeToFile:pathatomically:YES];
4.2、存储到手机的图片库中
- CGImageRef screen = UIGetScreenImage();
- UIImage* image = [UIImage imageWithCGImage:screen];
- CGImageRelease(screen);
- UIImageWriteToSavedPhoto
sAlbum(image, self, nil, nil);
获取当前app的名称和版本号
- NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];
- // app名称
- NSString *name = [infoDictionary objectForKey:@"CFBundleDisplayName"];
- // app版本
- NSString *version = [infoDictionary objectForKey:@"CFBundleShortVersionStri
ng" ]; - // app build版本
- NSString *build = [infoDictionary objectForKey:@"CFBundleVersion"];
UILabel根据text自动调整大小
- label.text = @"**********";
- CGRect frame = label.frame;
- frame.size.height = 10000; // 设置一个很大的高度
- label.frame = frame;
- [label sizeToFit];
- frame.size.height = label.frame.size.height;
- label.frame = frame;
直接拨打有分机号的电话
- [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"tel://01011112222,3333"]];
一些有关图像处理的代码片段
- (UIImage *)rescaleImage:(UIImage *)img ToSize:(CGSize)size; //图片缩放裁剪
- (UIImage*)transformWidth:(CGFloat)width height:(CGFloat)height; //改变大小
+ (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2; //合并图片
+ (UIImage *)imageFromImage:(UIImage *)image inRect:(CGRect)rect; //裁剪部分图片
+ (void)imageSavedToPhotosAlbum:(UIImage *)image
didFinishSavingWithError
零）重新设置图片的尺寸
- (UIImage *)rescaleImage:(UIImage *)img ToSize:(CGSize)size {
CGRect rect = CGRectMake(0.0, 0.0, size.width, size.height);
UIGraphicsBeginImageCont
[img drawInRect:rect]; // scales image to rect
UIImage *resImage = UIGraphicsGetImageFromCu
UIGraphicsEndImageContex
return resImage;
}
－）根据给定得图片，从其指定区域截取一张新得图片
-(UIImage *)getImageFromImage{
//大图bigImage
//定义myImageRect，截图的区域
CGRect myImageRect = CGRectMake(10.0, 10.0, 57.0, 57.0);
UIImage* bigImage= [UIImage imageNamed:@"k00030.jpg"];
CGImageRef imageRef = bigImage.CGImage;
CGImageRef subImageRef = CGImageCreateWithImageIn
CGSize size;
size.width = 57.0;
size.height = 57.0;
UIGraphicsBeginImageCont
CGContextRef context = UIGraphicsGetCurrentCont
CGContextDrawImage(context, myImageRect, subImageRef);
UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];
UIGraphicsEndImageContex
return smallImage;
}
二） 合并两张图片
- (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {
UIGraphicsBeginImageCont
// Draw image1
[image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];
// Draw image2
[image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];
UIImage *resultingImage = UIGraphicsGetImageFromCu
UIGraphicsEndImageContex
return resultingImage;
}
三） 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
+ (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：UIGraphicsBeginImageCont
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]; }
关于图片缩放的线程安全和非线程安全操作.
非线程安全的操作只能在主线程中进行操作,对于大图片的处理肯定会消耗大量的时间,如下面的方法
方法 1： 使用 UIKit
+ (UIImage*)imageWithImage INCLUDEPICTURE "http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif" \* MERGEFORMATINET UIImage*)image scaledToSize INCLUDEPICTURE "http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif" \* MERGEFORMATINET CGSize)newSize;
{
// Create a graphics image context
UIGraphicsBeginImageCont
// Tell the old image to draw in this new context, with the desired
// new size
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
// Get the new image from the context
UIImage* newImage = UIGraphicsGetImageFromCu
// End the context
UIGraphicsEndImageContex
// Return the new image.
return newImage;
}
此方法很简单， 但是，这种方法不是线程安全的情况下.
方法 2： 使用 CoreGraphics
+ (UIImage*)imageWithImage INCLUDEPICTURE "http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif" \* MERGEFORMATINET UIImage*)sourceImage scaledToSize INCLUDEPICTURE "http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif" \* MERGEFORMATINET CGSize)newSize; { CGFloat targetWidth = targetSize.width; CGFloat targetHeight = targetSize.height; CGImageRef imageRef = [sourceImage CGImage]; CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef); CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef); if (bitmapInfo == kCGImageAlphaNone) { bitmapInfo = kCGImageAlphaNoneSkipLas } CGContextRef bitmap; if (sourceImage.imageOrientation == UIImageOrientationUp ||sourceImage.imageOrientation == UIImageOrientationDown) { bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight,CGImageGetBitsPerCompone } else { bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth,CGImageGetBitsPerCompone } if (sourceImage.imageOrientation == UIImageOrientationLeft) { CGContextRotateCTM (bitmap, radians(90)); CGContextTranslateCTM (bitmap, 0, -targetHeight); } else if (sourceImage.imageOrientation ==UIImageOrientationRight) { CGContextRotateCTM (bitmap, radians(-90)); CGContextTranslateCTM (bitmap, -targetWidth, 0); } else if (sourceImage.imageOrientation == UIImageOrientationUp) { // NOTHING } else if (sourceImage.imageOrientation == UIImageOrientationDown){ CGContextTranslateCTM (bitmap, targetWidth, targetHeight); CGContextRotateCTM (bitmap, radians(-180.)); } CGContextDrawImage(bitmap, CGRectMake(0, 0, targetWidth,targetHeight), imageRef); CGImageRef ref = CGBitmapContextCreateIma UIImage* newImage = [UIImage imageWithCGImage:ref]; CGContextRelease(bitmap); CGImageRelease(ref); return newImage; } 这种方法的好处是它是线程安全，加上它负责的 （使用正确的颜色空间和位图信息，处理图像方向） 的小东西，UIKit 版本不会。 如何调整和保持长宽比 （如 AspectFill 选项）？ 它是非常类似于上述，方法，它看起来像这样： + (UIImage*)imageWithImage INCLUDEPICTURE "http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif" \* MERGEFORMATINET UIImage*)sourceImage scaledToSizeWithSameAspe { CGSize imageSize = sourceImage.size; CGFloat width = imageSize.width; CGFloat height = imageSize.height; CGFloat targetWidth = targetSize.width; CGFloat targetHeight = targetSize.height; CGFloat scaleFactor = 0.0; CGFloat scaledWidth = targetWidth; CGFloat scaledHeight = targetHeight; CGPoint thumbnailPoint = CGPointMake(0.0,0.0); if (CGSizeEqualToSize(imageSize, targetSize) == NO) { CGFloat widthFactor = targetWidth / width; CGFloat heightFactor = targetHeight / height; if (widthFactor > heightFactor) { scaleFactor = widthFactor; // scale to fit height } else { scaleFactor = heightFactor; // scale to fit width } scaledWidth = width * scaleFactor; scaledHeight = height * scaleFactor; // center the image if (widthFactor > heightFactor) { thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; } else if (widthFactor < heightFactor) { thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5; } } CGImageRef imageRef = [sourceImage CGImage]; CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef); CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef); if (bitmapInfo == kCGImageAlphaNone) { bitmapInfo = kCGImageAlphaNoneSkipLas } CGContextRef bitmap; if (sourceImage.imageOrientation == UIImageOrientationUp ||sourceImage.imageOrientation == UIImageOrientationDown) { bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight,CGImageGetBitsPerCompone } else { bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth,CGImageGetBitsPerCompone } // In the right or left cases, we need to switch scaledWidth and scaledHeight, // and also the thumbnail point if (sourceImage.imageOrientation == UIImageOrientationLeft) { thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x); CGFloat oldScaledWidth = scaledWidth; scaledWidth = scaledHeight; scaledHeight = oldScaledWidth; CGContextRotateCTM (bitmap, radians(90)); CGContextTranslateCTM (bitmap, 0, -targetHeight); } else if (sourceImage.imageOrientation ==UIImageOrientationRight) { thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x); CGFloat oldScaledWidth = scaledWidth; scaledWidth = scaledHeight; scaledHeight = oldScaledWidth; CGContextRotateCTM (bitmap, radians(-90)); CGContextTranslateCTM (bitmap, -targetWidth, 0); } else if (sourceImage.imageOrientation == UIImageOrientationUp) { // NOTHING } else if (sourceImage.imageOrientation == UIImageOrientationDown){ CGContextTranslateCTM (bitmap, targetWidth, targetHeight); CGContextRotateCTM (bitmap, radians(-180.)); } CGContextDrawImage(bitmap, CGRectMake(thumbnailPoint.x,thumbnailPoint.y, scaledWidth, scaledHeight), imageRef); CGImageRef ref = CGBitmapContextCreateIma UIImage* newImage = [UIImage imageWithCGImage:ref]; CGContextRelease(bitmap); CGImageRelease(ref); return newImage; } |
