UIGraphicsBeginImageContext

UIGraphicsBeginImageContext
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：

void UIGraphicsBeginImageContext(CGSize size);

参数size为新创建的位图上下文的大小。它同时是由UIGraphicsGetImageFromCurrentImageContext函数返回的图形大小。
该函数的功能同UIGraphicsBeginImageContextWithOptions的功能相同，相当与UIGraphicsBeginImageContextWithOptions的opaque参数为NO,scale因子为1.0。

UIGraphicsBeginImageContextWithOptions
函数原型为：

void UIGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque, CGFloat scale);

size——同UIGraphicsBeginImageContext
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

默认创建一个透明的位图上下文

 

UIImageC处理

1、等比缩放

C代码   

1. - (UIImage *) scaleImage:(UIImage *)image toScale:(float)scaleSize {
2. UIGraphicsBeginImageContext(CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize);
3. [image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height * scaleSize)];
4. UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
5. UIGraphicsEndImageContext();
6. return scaledImage;
7. }

 

2、自定义大小

C代码   

1. - (UIImage *) reSizeImage:(UIImage *)image toSize:(CGSize)reSize {
2. UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height));
3. [image drawInRect:CGRectMake(0, 0, reSize.width, reSize.height)];
4. UIImage *reSizeImage = UIGraphicsGetImageFromCurrentImageContext();
5. UIGraphicsEndImageContext();
6. return reSizeImage;
7. }

 

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

C代码   

1. -(UIImage*) captureView:(UIView *)theView {
2. CGRect rect = theView.frame;
3. UIGraphicsBeginImageContext(rect.size);
4. CGContextRef context = UIGraphicsGetCurrentContext();
5. [theView.layer renderInContext:context];
6. UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
7. UIGraphicsEndImageContext();
8. return img;
9. }

 

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

 

C代码   

1. NSString *path = [[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
2. [UIImagePNGRepresentation(image) writeToFile:pathatomically:YES];

4.2、存储到手机的图片库中

C代码   

1. CGImageRef screen = UIGetScreenImage();
2. UIImage* image = [UIImage imageWithCGImage:screen];
3. CGImageRelease(screen);
4. UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

 

 

 

获取当前app的名称和版本号

 

 

C代码   

1. NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];
2. // app名称
3. NSString *name = [infoDictionary objectForKey:@"CFBundleDisplayName"];
4. // app版本
5. NSString *version = [infoDictionary objectForKey:@"CFBundleShortVersionString"];
6. // app build版本
7. NSString *build = [infoDictionary objectForKey:@"CFBundleVersion"];

 

 

UILabel根据text自动调整大小

 

C代码   

1. label.text = @"**********";
2. CGRect frame = label.frame;
3. frame.size.height = 10000; // 设置一个很大的高度
4. label.frame = frame;
5. [label sizeToFit];
6. frame.size.height = label.frame.size.height;
7. label.frame = frame;

 

 

直接拨打有分机号的电话

 

C代码   

1. [[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:(NSError *)error contextInfo:(void *)contextInfo; //保存图片到媒体库

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);

UIGraphicsBeginImageContext(rect.size);

[img drawInRect:rect]; // scales image to rect

UIImage *resImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

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 = CGImageCreateWithImageInRect(imageRef, myImageRect);

CGSize size;

size.width = 57.0;

size.height = 57.0;

UIGraphicsBeginImageContext(size);

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextDrawImage(context, myImageRect, subImageRef);

UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];

UIGraphicsEndImageContext();

return smallImage;

}

二） 合并两张图片

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

UIGraphicsBeginImageContext(image1.size);

// 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 = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

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：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。

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

UIGraphicsBeginImageContext(newSize);

// 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 = UIGraphicsGetImageFromCurrentImageContext();

// End the context

UIGraphicsEndImageContext();

// 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 = kCGImageAlphaNoneSkipLast; } CGContextRef bitmap; if (sourceImage.imageOrientation == UIImageOrientationUp ||sourceImage.imageOrientation == UIImageOrientationDown) { bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight,CGImageGetBitsPerComponent(imageRef),CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo); } else { bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth,CGImageGetBitsPerComponent(imageRef),CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo); } 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 = CGBitmapContextCreateImage(bitmap); 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 scaledToSizeWithSameAspectRatio INCLUDEPICTURE "http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif" \* MERGEFORMATINET CGSize)targetSize; { 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 = kCGImageAlphaNoneSkipLast; } CGContextRef bitmap; if (sourceImage.imageOrientation == UIImageOrientationUp ||sourceImage.imageOrientation == UIImageOrientationDown) { bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight,CGImageGetBitsPerComponent(imageRef),CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo); } else { bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth,CGImageGetBitsPerComponent(imageRef),CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo); } // 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 = CGBitmapContextCreateImage(bitmap); UIImage* newImage = [UIImage imageWithCGImage:ref]; CGContextRelease(bitmap); CGImageRelease(ref); return newImage; }

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