UIImageView自适应图片大小

窗口大小获取: CGRect screenBounds = [ [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(, , , ); imageView.layer.cornerRadius = ; imageView.layer.masksToBounds = YES; //自适应图片宽高比例 imageView1.contentMode = UIViewContentModeScaleAspectFit; 二 图片自适应UIImageView - (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; //保存图片到媒体库 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 ： 使用 UIKit + (UIImage*)imageWithImage :( UIImage*)image scaledToSize :(CGSize)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(,,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 ： 使用 CoreGraphics + (UIImage*)imageWithImage :( UIImage*)sourceImage scaledToSize :(CGSize)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());
CGContextTranslateCTM (bitmap, , -targetHeight); } else if (sourceImage.imageOrientation ==UIImageOrientationRight) {
CGContextRotateCTM (bitmap, radians(-));
CGContextTranslateCTM (bitmap, -targetWidth, ); } else if (sourceImage.imageOrientation == UIImageOrientationUp) { // NOTHING } else if (sourceImage.imageOrientation == UIImageOrientationDown){ CGContextTranslateCTM (bitmap, targetWidth, targetHeight);
CGContextRotateCTM (bitmap, radians(-.)); } CGContextDrawImage(bitmap, CGRectMake(, , targetWidth,targetHeight), imageRef);
CGImageRef ref = 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*)imageWithImage :( UIImage*)sourceImage scaledToSizeWithSameAspectRatio :( CGSize)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;
}
else if (widthFactor < heightFactor) {
thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
}
}
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);
} // In the right or left cases, we need to switch scaledWidth and scaledHeight,
// and also the thumbnail point
if (sourceImage.imageOrientation == UIImageOrientationLeft) {
thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x);
CGFloat oldScaledWidth = scaledWidth;
scaledWidth = scaledHeight;
scaledHeight = oldScaledWidth;
CGContextRotateCTM (bitmap, radians());
CGContextTranslateCTM (bitmap, , -targetHeight);
} else if (sourceImage.imageOrientation ==UIImageOrientationRight) {
thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x);
CGFloat oldScaledWidth = scaledWidth;
scaledWidth = scaledHeight;
scaledHeight = oldScaledWidth;
CGContextRotateCTM (bitmap, radians(-));
CGContextTranslateCTM (bitmap, -targetWidth, );
} else if (sourceImage.imageOrientation == UIImageOrientationUp) { // NOTHING } else if (sourceImage.imageOrientation == UIImageOrientationDown){
CGContextTranslateCTM (bitmap, targetWidth, targetHeight);
CGContextRotateCTM (bitmap, radians(-.));
} CGContextDrawImage(bitmap, CGRectMake(thumbnailPoint.x,thumbnailPoint.y, scaledWidth, scaledHeight), imageRef);
CGImageRef ref = CGBitmapContextCreateImage(bitmap);
UIImage* newImage = [UIImage imageWithCGImage:ref];
CGContextRelease(bitmap);
CGImageRelease(ref);
return newImage;
}