UIGraphicsBeginImageContext
創建一個基於位圖的上下文（context）,並將其設置爲當前上下文(context)。方法聲明如下：
void UIGraphicsBeginImageContext(CGSize size);
參數size爲新創建的位圖上下文的大小。它同時是由UIGraphicsGetImageFromCurrentImageContext函數返回的圖形大小。
該函數的功能同UIGraphicsBeginImageContextWithOptions的功能相同，相當與UIGraphicsBeginImageContextWithOptions的opaque參數爲NO,scale因子爲1.0。
UIGraphicsBeginImageContextWithOptions
函數原型爲：
void UIGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque, CGFloat scale);
size——同UIGraphicsBeginImageContext
opaque—透明開關，如果圖形完全不用透明，設置爲YES以優化位圖的存儲。
scale—–縮放因子
UIImageC處理
1、等比縮放
- - (UIImage *) scaleImage:(UIImage *)image toScale:(float)scaleSize {
- UIGraphicsBeginImageContext(CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize);
- [image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height * scaleSize)];
- UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
- UIGraphicsEndImageContext();
- return scaledImage;
- }
2、自定義大小
- - (UIImage *) reSizeImage:(UIImage *)image toSize:(CGSize)reSize {
- UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height));
- [image drawInRect:CGRectMake(0, 0, reSize.width, reSize.height)];
- UIImage *reSizeImage = UIGraphicsGetImageFromCurrentImageContext();
- UIGraphicsEndImageContext();
- return reSizeImage;
- }
3、處理某個特定的view
只要是繼承UIView的object 都可以處理
必須先import QuzrtzCore.framework
- -(UIImage*) captureView:(UIView *)theView {
- CGRect rect = theView.frame;
- UIGraphicsBeginImageContext(rect.size);
- CGContextRef context = UIGraphicsGetCurrentContext();
- [theView.layer renderInContext:context];
- UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
- UIGraphicsEndImageContext();
- return img;
- }
4、存儲圖片
4.1、存儲到app的文件裏
把要處理的圖片以image.png的名字存儲到app home地下的Document目錄中
- NSString *path = [[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
- [UIImagePNGRepresentation(image) writeToFile:pathatomically:YES];
4.2、存儲到手機的圖片庫中
- CGImageRef screen = UIGetScreenImage();
- UIImage* image = [UIImage imageWithCGImage:screen];
- CGImageRelease(screen);
- UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);
獲取當前app的名稱和版本號
- NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];
- // app名稱
- NSString *name = [infoDictionary objectForKey:@"CFBundleDisplayName"];
- // app版本
- NSString *version = [infoDictionary objectForKey:@"CFBundleShortVersionString"];
- // app build版本
- NSString *build = [infoDictionary objectForKey:@"CFBundleVersion"];
UILabel根據text自動調整大小
- label.text = @"**********";
- CGRect frame = label.frame;
- frame.size.height = 10000; // 設置一個很大的高度
- label.frame = frame;
- [label sizeToFit];
- frame.size.height = label.frame.size.height;
- label.frame = frame;
直接撥打有分機號的電話
- [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"tel://01011112222,3333"]];
一些有關圖像處理的代碼片段
- (UIImage *)rescaleImage:(UIImage *)img ToSize:(CGSize)size; //圖片縮放裁剪
- (UIImage*)transformWidth:(CGFloat)width height:(CGFloat)height; //改變大小
+ (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2; //合併圖片
+ (UIImage *)imageFromImage:(UIImage *)image inRect:(CGRect)rect; //裁剪部分圖片
+ (void)imageSavedToPhotosAlbum:(UIImage *)image
didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo; //保存圖片到媒體庫
零）重新設置圖片的尺寸
- (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;
}
－）根據給定得圖片，從其指定區域截取一張新得圖片
-(UIImage *)getImageFromImage{
//大圖bigImage
//定義myImageRect，截圖的區域
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） 合併兩張圖片
- (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） 捕捉屏幕截圖
CALayer實例使用Core Graphics的renderInContext方法可以將視圖繪製到圖像上下文中以便轉化爲其他UIImage實例。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)創建一個基於位圖的上下文(context)，並將其設置爲當前上下文。函數功能與UIGraphicsBeginImageContextWithOptions相同，相當於該方法的opaque參數爲NO，scale因子爲1.0。而UIGraphicsEndImageContext()方法是移除棧頂的基於當前位圖的圖形上下文。
視圖添加倒影效果
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); //倒影層框架設置，其中高度是原視圖的百分比 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創建倒影
+ (CGImageRef) createGradientImage:(CGSize)size { CGFloat colors[] = {0.0,1.0,1.0,1.0}; //在灰色設備色彩上建立一漸變 CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); CGContextRef context = CGBitmapContextCreate(nil,size.width,size.height,8,0,colorSpace,kCGImageAlphaNone); CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace,colors,NULL,2); CGColorSpaceRelease(colorSpace); //繪製線性漸變 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]; }
關於圖片縮放的線程安全和非線程安全操作.
非線程安全的操作只能在主線程中進行操作,對於大圖片的處理肯定會消耗大量的時間,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;
}
此方法很簡單， 但是，這種方法不是線程安全的情況下.
方法 2： 使用 CoreGraphics
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+ (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; } 這種方法的好處是它是線程安全，加上它負責的 （使用正確的顏色空間和位圖信息，處理圖像方向） 的小東西，UIKit 版本不會。 如何調整和保持長寬比 （如 AspectFill 選項）？ 它是非常類似於上述，方法，它看起來像這樣： + (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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