iPhone处理图片(UIImage扩展类) 自动适应frame大小方法

NSData *imgData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"图片地址"]];

UIImage *tempImg = [UIImage imageWithData:imgData];

UIImageView *img = [[UIImageView alloc] initWithFrame:CGRectMake(15, 20, 60, 80)];

img.image = tempImg;

//[img initWithImage:tempImg]; 用这个不行,为什么?

[tempImg rescaleImageToSize:CGSizeMake(60, 80)];

[self.view addSubView: img];

 

下面这个方法 可以改变图片大小 自适应,自己传参数吧

- (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

UIImageExtras

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*)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(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*)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(90));

CGContextTranslateCTM (bitmap, 0, -targetHeight);

} else if (sourceImage.imageOrientation ==UIImageOrientationRight) {

CGContextRotateCTM (bitmap, radians(-90));

CGContextTranslateCTM (bitmap, -targetWidth, 0);

} else if (sourceImage.imageOrientation == UIImageOrientationUp) {

// NOTHING

} else if (sourceImage.imageOrientation == UIImageOrientationDown){

CGContextTranslateCTM (bitmap, targetWidth, targetHeight);

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

}

CGContextDrawImage(bitmap, CGRectMake(0, 0, 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(90));

CGContextTranslateCTM (bitmap, 0, -targetHeight);

} else if (sourceImage.imageOrientation ==UIImageOrientationRight) {

thumbnailPoint = CGPointMake(thumbnailPoint.y, thumbnailPoint.x);

CGFloat oldScaledWidth = scaledWidth;

scaledWidth = scaledHeight;

scaledHeight = oldScaledWidth;

CGContextRotateCTM (bitmap, radians(-90));

CGContextTranslateCTM (bitmap, -targetWidth, 0);

} else if (sourceImage.imageOrientation == UIImageOrientationUp) {

// NOTHING

} else if (sourceImage.imageOrientation == UIImageOrientationDown){

CGContextTranslateCTM (bitmap, targetWidth, targetHeight);

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

}

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;

}