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UIGraphicsBeginImageContext系列知识

(2012-10-30 14:08:51)
标签：

杂谈

 分类： IOS学习

 

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

  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. }
- (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、自定义大小

  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. }
- (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、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

  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. }
-(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

 

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

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

 

 

  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"];
    NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];
    // app名称
    NSString *name = [infoDictionary objectForKey:@"CFBundleDisplayName"];
    // app版本
    NSString *version = [infoDictionary objectForKey:@"CFBundleShortVersionString"];
    // app build版本
    NSString *build = [infoDictionary objectForKey:@"CFBundleVersion"];

 

 

UILabel根据text自动调整大小

 

  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;
    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

 

  1. [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"tel://01011112222,3333"]];
[[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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