UIGraphicsBeginImageContext系列知识
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：
voidUIGraphicsBeginImageContext(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：
voidUIGraphicsBeginImageContextWithOptions(CGSize size,BOOLopaque, 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
UIImageC处理
1、等比缩放
- (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();
returnscaledImage;
}
2、自定义大小
代码
- (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();
returnreSizeImage;
}
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
代码
-(UIImage*) captureView:(UIView *)theView
{
CGRect rect = theView.frame;
UIGraphicsBeginImageContext(rect.size);
CGContextRef context =UIGraphicsGetCurrentContext();
[theView.layer renderInContext:context];
UIImage *img =UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
returnimg;
}
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
代码
NSString *path =[[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
[UIImagePNGRepresentation(image)writeToFile:pathatomically:YES];
4.2、存储到手机的图片库中
代码
CGImageRef screen =
UIGetScreenImage();
UIImage* image = [UIImage
imageWithCGImage:screen];
CGImageRelease(screen);
UIImageWriteToSavedPhotosAlbum(image, self, nil,nil);
获取当前app的名称和版本号
代码
NSDictionary *infoDictionary = [[NSBundle
mainBundle] infoDictionary];
//app名称
NSString *name = [infoDictionaryobjectForKey:@"CFBundleDisplayName"];
//app版本
NSString *version = [infoDictionaryobjectForKey:@"CFBundleShortVersionString"];
// app build版本
NSString *build = [infoDictionaryobjectForKey:@"CFBundleVersion"];
UILabel根据text自动调整大小
代码
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
代码
[[UIApplication sharedApplication] openURL:[NSURL
URLWithString:@"tel://01011112222,3333"]];
- (UIImage *)rescaleImage:(UIImage *)img ToSize:(CGSize)size;//图片缩放裁剪
- (UIImage*)transformWidth:(CGFloat)widthheight:(CGFloat)height; //改变大小
+ (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage*)image2; //合并图片
+ (UIImage *)imageFromImage:(UIImage *)imageinRect:(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();
returnresultingImage;
}
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(CGSizesize)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*)imageWithImageINCLUDEPICTURE"http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif"\* MERGEFORMATINET UIImage*)sourceImagescaledToSizeWithSameAspectRatio 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;
}
