UIimageView图片自适应大小

叹落花 2015-01-11

展开全文

窗口大小获取：

CGRectscreenBounds = [ [UIScreenmainScreen]bounds];//返回的是带有状态栏的Rect

CGRect rect = [ [UIScreenmainScreen]applicationFrame];//不包含状态栏的Rect

UIImageView：

一：圆角以及自适应图片大小

UIImage* image = [UIImage imageNamed:@"image.png"];

UIImageView* imageView = [[[UIImageView alloc] initWithImage:image] autorelease];

imageView.frame = CGRectMake(0, 0, 300, 200);

imageView.layer.cornerRadius = 8;

imageView.layer.masksToBounds = YES;

//自适应图片宽高比例

imageView1.contentMode = UIViewContentModeScaleAspectFit;

二图片自适应UIImageView (来源于:http://www./Mobile/iPhone/201103/29636.html)

- (UIImage *)rescaleImageToSize:(CGSize)size {

CGRect rect = CGRectMake(0.0, 0.0, size.width, size.height);

UIGraphicsBeginImageContext(rect.size);

[self drawInRect:rect]; // scales image to rect

UIImage *resImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return resImage;

}

- (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize; //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; //保存库图片到媒体

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*)imageWithImageUIImage*)image scaledToSizeCGSize)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*)imageWithImageUIImage*)sourceImage scaledToSizeCGSize)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);

}elseif(sourceImage.imageOrientation ==UIImageOrientationRight){

CGContextRotateCTM(bitmap, radians(-90));

CGContextTranslateCTM(bitmap,-targetWidth,0);

}elseif(sourceImage.imageOrientation ==UIImageOrientationUp){

// NOTHING

}elseif(sourceImage.imageOrientation ==UIImageOrientationDown){

CGContextTranslateCTM(bitmap, targetWidth, targetHeight);

CGContextRotateCTM(bitmap, radians(-180.));

}

CGContextDrawImage(bitmap,CGRectMake(0,0, targetWidth,targetHeight), imageRef);

CGImageRefref=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*)imageWithImageUIImage*)sourceImage scaledToSizeWithSameAspectRatioCGSize)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;

}

elseif(widthFactor < heightFactor){

thumbnailPoint.x =(targetWidth - scaledWidth)*0.5;

}