UIImage 图片处理:截图,缩放,设定大小,存储

图片的处理大概分 截图(capture), 缩放(scale), 设定大小(resize), 存储(save)

1.等比率缩放

- (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();
return scaledImage;
}

2.自定长宽

- (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View
只要是继承UIView的object 都可以处理
必须先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.储存图片
储存图片这里分成储存到app的文件里和储存到手机的图片库里

  1. 储存到app的文件里
NSString *path = [[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
[UIImagePNGRepresentation(image) writeToFile:pathatomically:YES];

把要处理的图片, 以image.png名称存到app home下的Documents目录里
2)储存到手机的图片库里(必须在真机使用,模拟器无法使用)

CGImageRef screen = UIGetScreenImage();
UIImage* image = [UIImage imageWithCGImage:screen];
CGImageRelease(screen);
UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);
UIGetScreenImage(); // 原来是private(私有)api, 用来截取整个画面,不过SDK 4.0后apple就开放了

Quartz Framework Core Graphics

以下代码用到了Quartz Framework 和 Core Graphics Framework. 在workspace的framework目录里添加这两个framework.在UIKit里,图像类UIImage和CGImageRef的画图操作都是通过Graphics Context来完成。Graphics Context封装了变换的参数,使得在不同的坐标系里操作图像非常方便。缺点就是,获取图像的数据不是那么方便。下面会给出获取数据区的代码。

  1. 从UIView中获取图像相当于窗口截屏。
    (ios提供全局的全屏截屏函数UIGetScreenView(). 如果需要特定区域的图像,可以crop一下)
CGImageRef screen = UIGetScreenImage();
UIImage* image = [UIImage imageWithCGImage:screen];
  1. 对于特定UIView的截屏。
    (可以把当前View的layer,输出到一个ImageContext中,然后利用这个ImageContext得到UIImage)
-(UIImage*)captureView: (UIView *)theView
{
CGRect rect = theView.frame;
UIGraphicsBeginImageContext(rect.size);
CGContextRef context =UIGraphicsGetCurrentContext();
[theView.layer renderInContext:context];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return img;
}
  1. 如果需要裁剪指定区域。
    (可以path & clip,以下例子是建一个200x200的图像上下文,再截取出左上角)
UIGraphicsBeginImageContext(CGMakeSize(200,200));
CGContextRefcontext=UIGraphicsGetCurrentContext();
UIGraphicsPushContext(context);
// ...把图写到context中,省略[indent]CGContextBeginPath();
CGContextAddRect(CGMakeRect(0,0,100,100));
CGContextClosePath();[/indent]CGContextDrawPath();
CGContextFlush(); // 强制执行上面定义的操作
UIImage* image = UIGraphicGetImageFromCurrentImageContext();
UIGraphicsPopContext();
  1. 存储图像。
    (分别存储到home目录文件和图片库文件。)
    存储到目录文件是这样
NSString *path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"image.png"];
[UIImagePNGRepresentation(image) writeToFile:path atomically:YES];

若要存储到图片库里面

UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
  1. 互相转换UImage和CGImage。
    (UImage封装了CGImage, 互相转换很容易)
UIImage* imUI=nil;
CGImageRef imCG=nil;
imUI = [UIImage initWithCGImage:imCG];
imCG = imUI.CGImage;
  1. 从CGImage上获取图像数据区。
    (在apple dev上有QA, 不过好像还不支持ios)

下面给出一个在ios上反色的例子

-(id)invertContrast:(UIImage*)img
{
CGImageRef inImage = img.CGImage; 
CGContextRef ctx;
CFDataRef m_DataRef;
m_DataRef = CGDataProviderCopyData(CGImageGetDataProvider(inImage)); 

int width = CGImageGetWidth( inImage );
int height = CGImageGetHeight( inImage );

int bpc = CGImageGetBitsPerComponent(inImage);
int bpp = CGImageGetBitsPerPixel(inImage);
int bpl = CGImageGetBytesPerRow(inImage);

UInt8 * m_PixelBuf = (UInt8 *) CFDataGetBytePtr(m_DataRef);
int length = CFDataGetLength(m_DataRef);

NSLog(@"len %d", length);
NSLog(@"width=%d, height=%d", width, height);
NSLog(@"1=%d, 2=%d, 3=%d", bpc, bpp,bpl);

for (int index = 0; index < length; index += 4)
{ 
m_PixelBuf[index + 0] = 255 - m_PixelBuf[index + 0];// b
m_PixelBuf[index + 1] = 255 - m_PixelBuf[index + 1];// g
m_PixelBuf[index + 2] = 255 - m_PixelBuf[index + 2];// r
}

ctx = CGBitmapContextCreate(m_PixelBuf, width, height, bpb, bpl, CGImageGetColorSpace( inImage ), kCGImageAlphaPremultipliedFirst );
CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
UIImage* rawImage = [UIImage imageWithCGImage:imageRef];
CGContextRelease(ctx);
return rawImage;
}
  1. 显示图像数据区。
    (显示图像数据区,也就是unsigned char*转为graphics context或者UIImage或和CGImageRef)
CGContextRef ctx = CGBitmapContextCreate(pixelBuf,width,height, bitsPerComponent,bypesPerLine, colorSpace,kCGImageAlphaPremultipliedLast );
CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
UIImage* image = [UIImage imageWithCGImage:imageRef];
NSString* path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"ss.png"];
[UIImagePNGRepresentation(self.image) writeToFile:path atomically:YES];
CGContextRelease(ctx);

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