iphone iPhone开发应用UIImage图片对象操作

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原文链接：http://www.cnblogs.com/85538649/archive/2011/12/06/2278547.html

本文详细介绍了在iOS开发应用中如何操作UIImage图片对象，包括从指定区域截取图片、常用缩放方法、调整图片大小及旋转等操作。通过代码实现，帮助开发者更好地理解和运用UIImage的特性。

1原文摘自：http://mobile.51cto.com/iphone-284346.htm

iPhone开发应用UIImage图片对象操作是本文要介绍的内容，主要来学习UIImage图片对象操作，内容不多，主要是以代码实现图片对象的操作。

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;
boundsbounds.size.height = bounds.size.width / ratio;
}
else
{
bounds.size.height = maxHeight;
boundsbounds.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;
boundsbounds.size.height = bounds.size.width / ratio;
}
else
{
bounds.size.height = kMaxResolution;
boundsbounds.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;
boundsbounds.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;
boundsbounds.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;
boundsbounds.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;
boundsbounds.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;
}

小结：iPhone开发应用UIImage图片对象操作的内容介绍完了，希望通过本文的学习能对你有所帮助！

转载于:https://www.cnblogs.com/85538649/archive/2011/12/06/2278547.html