iOS图片处理,截图,缩放,存储

ngmm的头像 ngmm 15 2015-06-07 23:00 0

 基本信息

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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

//====================================================================================

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)

  1. CGImageRef screen = UIGetScreenImage();
  2. UIImage* image = [UIImage imageWithCGImage:screen];

2. 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)

  1. -(UIImage*)captureView: (UIView *)theView
  2. {
  3. CGRect rect = theView.frame;
  4. UIGraphicsBeginImageContext(rect.size);
  5. CGContextRef context =UIGraphicsGetCurrentContext();
  6. [theView.layer renderInContext:context];
  7. UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
  8. UIGraphicsEndImageContext();

  9. return img;
  10. }

3. 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)

  1. UIGraphicsBeginImageContext(CGMakeSize(200,200));
  2. CGContextRefcontext=UIGraphicsGetCurrentContext();
  3. UIGraphicsPushContext(context);
  4. // ...把图写到context中,省略[indent]CGContextBeginPath();
  5. CGContextAddRect(CGMakeRect(0,0,100,100));
  6. CGContextClosePath();[/indent]CGContextDrawPath();
  7. CGContextFlush(); // 强制执行上面定义的操作
  8. UIImage* image = UIGraphicGetImageFromCurrentImageContext();
  9. UIGraphicsPopContext();

4. 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

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

若要存储到图片库里面

  1. UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);


5.  互相转换UImage和CGImage。

(UImage封装了CGImage, 互相转换很容易)

  1. UIImage* imUI=nil;
  2. CGImageRef imCG=nil;
  3. imUI = [UIImage initWithCGImage:imCG];
  4. imCG = imUI.CGImage;

6. 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

  1. -(id)invertContrast:(UIImage*)img
  2. {
  3. CGImageRef inImage = img.CGImage; 
  4. CGContextRef ctx;
  5. CFDataRef m_DataRef;
  6. m_DataRef = CGDataProviderCopyData(CGImageGetDataProvider(inImage)); 

  7. int width = CGImageGetWidth( inImage );
  8. int height = CGImageGetHeight( inImage );

  9. int bpc = CGImageGetBitsPerComponent(inImage);
  10. int bpp = CGImageGetBitsPerPixel(inImage);
  11. int bpl = CGImageGetBytesPerRow(inImage);

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

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

  17. for (int index = 0; index < length; index += 4)
  18. m_PixelBuf[index + 0] = 255 - m_PixelBuf[index + 0];// b
  19. m_PixelBuf[index + 1] = 255 - m_PixelBuf[index + 1];// g
  20. m_PixelBuf[index + 2] = 255 - m_PixelBuf[index + 2];// r
  21. }

  22. ctx = CGBitmapContextCreate(m_PixelBuf, width, height, bpb, bpl, CGImageGetColorSpace( inImage ), kCGImageAlphaPremultipliedFirst );
  23. CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
  24. UIImage* rawImage = [UIImage imageWithCGImage:imageRef];
  25. CGContextRelease(ctx);
  26. return rawImage;
  27. }

 

7. 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)

  1. CGContextRef ctx = CGBitmapContextCreate(pixelBuf,width,height, bitsPerComponent,bypesPerLine, colorSpace,kCGImageAlphaPremultipliedLast );
  2. CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
  3. UIImage* image = [UIImage imageWithCGImage:imageRef];
  4. NSString* path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"ss.png"];
  5. [UIImagePNGRepresentation(self.image) writeToFile:path atomically:YES];
  6. CGContextRelease(ctx);
得到图像数据区后就可以很方便的实现图像处理的算法。
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