iphone UIImage用法介绍

红太狼 2022-09-18 12:57 142阅读 0赞

# iphone UIImage用法介绍 #

1.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;   
\}   
  
2.针对ＵIImage得一些常用缩放得方法：   
\-(UIImage\*)resizedImage1:(UIImage\*)inImage inRect:(CGRect)thumbRect \{   
 // Creates a bitmap-based graphics context and makes it the current context.   
 UIGraphicsBeginImageContext(thumbRect.size);   
 \[inImage drawInRect:thumbRect\];   
 return UIGraphicsGetImageFromCurrentImageContext();   
\}   
\-(UIImage\*)resizedImage2:(UIImage\*)inImage inRect:(CGRect)thumbRect \{   
 CGImageRef imageRef = \[inImage CGImage\];   
 CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);   
 /\* There's a wierdness with kCGImageAlphaNone and CGBitmapContextCreate   
 see Supported Pixel Formats in the Quartz 2D Programming Guide   
 Creating a Bitmap Graphics Context section   
 only RGB 8 bit images with alpha of kCGImageAlphaNoneSkipFirst, kCGImageAlphaNoneSkipLast, kCGImageAlphaPremultipliedFirst,and kCGImageAlphaPremultipliedLast, with a few other oddball image kinds are supported   
The images on input here are likely to be png or jpeg files\*/   
 if (alphaInfo == kCGImageAlphaNone)   
 alphaInfo = kCGImageAlphaNoneSkipLast;   
 // Build a bitmap context that's the size of the thumbRect   
 CGFloat bytesPerRow;   
 if( thumbRect.size.width > thumbRect.size.height ) \{   
 bytesPerRow = 4 \* thumbRect.size.width;   
 \} else \{   
 bytesPerRow = 4 \* thumbRect.size.height;   
 \}   
 CGContextRef bitmap = CGBitmapContextCreate(NULL,   
 thumbRect.size.width, // width   
 thumbRect.size.height, // height   
 8, //CGImageGetBitsPerComponent(imageRef), // really needs to always be 8   
 bytesPerRow, //4 \* thumbRect.size.width, // rowbytes   
 CGImageGetColorSpace(imageRef),   
 alphaInfo   
);   
 // Draw into the context, this scales the image   
 CGContextDrawImage(bitmap, thumbRect, imageRef);   
 // Get an image from the context and a UIImage   
 CGImageRef ref = CGBitmapContextCreateImage(bitmap);   
 UIImage\* result = \[UIImage imageWithCGImage:ref\];   
 CGContextRelease(bitmap); // ok if NULL   
 CGImageRelease(ref);   
 return result;   
\}   
\- (UIImage \*)scaleImage:(UIImage \*) image maxWidth:(float) maxWidth maxHeight:(float) maxHeight   
\{   
 CGImageRef imgRef = image.CGImage;   
 CGFloat width = CGImageGetWidth(imgRef);   
 CGFloat height = CGImageGetHeight(imgRef);   
 if (width <= maxWidth && height <= maxHeight)   
 \{   
 return image;   
 \}   
 CGAffineTransform transform = CGAffineTransformIdentity;   
 CGRect bounds = CGRectMake(0, 0, width, height);   
 if (width > maxWidth || height > maxHeight)   
 \{   
 CGFloat ratio = width/height;   
 if (ratio > 1)   
 \{   
 bounds.size.width = maxWidth;   
 bounds.size.height = bounds.size.width / ratio;   
 \}   
 else   
 \{   
 bounds.size.height = maxHeight;   
 bounds.size.width = bounds.size.height \* ratio;   
 \}   
 \}   
 CGFloat scaleRatio = bounds.size.width / width;   
 UIGraphicsBeginImageContext(bounds.size);   
 CGContextRef context = UIGraphicsGetCurrentContext();   
 CGContextScaleCTM(context, scaleRatio, -scaleRatio);   
 CGContextTranslateCTM(context, 0, -height);   
 CGContextConcatCTM(context, transform);   
 CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);   
 UIImage \*imageCopy = UIGraphicsGetImageFromCurrentImageContext();   
 UIGraphicsEndImageContext();   
 return imageCopy;   
\}   
  
3.其他缩放uiimage的size，有需要的可以看看   
\-(UIImage\*) scaleAndRotateImage:(UIImage\*)photoimage:(CGFloat)bounds\_width:(CGFloat)bounds\_height   
\{   
 //int kMaxResolution = 300;   
 CGImageRef imgRef =photoimage.CGImage;   
 CGFloat width = CGImageGetWidth(imgRef);   
 CGFloat height = CGImageGetHeight(imgRef);   
 CGAffineTransform transform = CGAffineTransformIdentity;   
 CGRect bounds = CGRectMake(0, 0, width, height);   
 /\*if (width > kMaxResolution || height > kMaxResolution)   
 \{   
 CGFloat ratio = width/height;   
 if (ratio > 1)   
 \{   
 bounds.size.width = kMaxResolution;   
 bounds.size.height = bounds.size.width / ratio;   
 \}   
 else   
 \{   
 bounds.size.height = kMaxResolution;   
 bounds.size.width = bounds.size.height \* ratio;   
 \}   
 \}\*/   
 bounds.size.width = bounds\_width;   
 bounds.size.height = bounds\_height;   
 CGFloat scaleRatio = bounds.size.width / width;   
 CGFloat scaleRatioheight = bounds.size.height / height;   
 CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));   
 CGFloat boundHeight;   
 UIImageOrientation orient =photoimage.imageOrientation;   
 switch(orient)   
 \{   
 case UIImageOrientationUp: //EXIF = 1   
 transform = CGAffineTransformIdentity;   
 break;   
 case UIImageOrientationUpMirrored: //EXIF = 2   
 transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);   
 transform = CGAffineTransformScale(transform, -1.0, 1.0);   
 break;   
 case UIImageOrientationDown: //EXIF = 3   
 transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);   
 transform = CGAffineTransformRotate(transform, M\_PI);   
 break;   
 case UIImageOrientationDownMirrored: //EXIF = 4   
 transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);   
 transform = CGAffineTransformScale(transform, 1.0, -1.0);   
 break;   
 case UIImageOrientationLeftMirrored: //EXIF = 5   
 boundHeight = bounds.size.height;   
 bounds.size.height = bounds.size.width;   
 bounds.size.width = boundHeight;   
 transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);   
 transform = CGAffineTransformScale(transform, -1.0, 1.0);   
 transform = CGAffineTransformRotate(transform, 3.0 \* M\_PI / 2.0);   
 break;   
 case UIImageOrientationLeft: //EXIF = 6   
 boundHeight = bounds.size.height;   
 bounds.size.height = bounds.size.width;   
 bounds.size.width = boundHeight;   
 transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);   
 transform = CGAffineTransformRotate(transform, 3.0 \* M\_PI / 2.0);   
 break;   
 case UIImageOrientationRightMirrored: //EXIF = 7   
 boundHeight = bounds.size.height;   
 bounds.size.height = bounds.size.width;   
 bounds.size.width = boundHeight;   
 transform = CGAffineTransformMakeScale(-1.0, 1.0);   
 transform = CGAffineTransformRotate(transform, M\_PI / 2.0);   
 break;   
 case UIImageOrientationRight: //EXIF = 8   
 boundHeight = bounds.size.height;   
 bounds.size.height = bounds.size.width;   
 bounds.size.width = boundHeight;   
 transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);   
 transform = CGAffineTransformRotate(transform, M\_PI / 2.0);   
 break;   
 default:   
 \[NSException raise:NSInternalInconsistencyException format:@"Invalid?image?orientation"\];   
 break;   
 \}   
 UIGraphicsBeginImageContext(bounds.size);   
 CGContextRef context = UIGraphicsGetCurrentContext();   
 if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft)   
 \{   
 CGContextScaleCTM(context, -scaleRatio, scaleRatioheight);   
 CGContextTranslateCTM(context, -height, 0);   
 \}   
 else   
 \{   
 CGContextScaleCTM(context, scaleRatio, -scaleRatioheight);   
 CGContextTranslateCTM(context, 0, -height);   
 \}   
 CGContextConcatCTM(context, transform);   
 CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);   
 UIImage \*imageCopy = UIGraphicsGetImageFromCurrentImageContext();   
 UIGraphicsEndImageContext();   
 return imageCopy;   
\}