ios--图片处理(修改、保存)UIGraphicsBeginImageContext

怼烎@ 2022-09-21 01:06 221阅读 0赞

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);

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

### UIImageC处理 ###

1、等比缩放

C代码

- (UIImage \*) scaleImage:(UIImage \*)image toScale:( float )scaleSize \{

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

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][Link 1] #

\- (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;