目前使用過的圖片裁剪方法
1、等比例壓縮 裁剪出的圖片是以asize最小值為邊框的正方形圖片
//修改圖片尺寸 同比縮放
+ (UIImage *)thumbnailWithImageWithoutScale:(UIImage *)image size:(CGSize)asize
{
UIImage *newimage;
if (nil == image) {
newimage = nil;
}
else{
CGSize oldsize = image.size;
CGRect rect;
if (asize.width/asize.height > oldsize.width/oldsize.height) {
rect.size.width = asize.height*oldsize.width/oldsize.height;
rect.size.height = asize.height;
rect.origin.x = (asize.width - rect.size.width)/2;
rect.origin.y = 0;
}
else{
rect.size.width = asize.width;
rect.size.height = asize.width*oldsize.height/oldsize.width;
rect.origin.x = 0;
rect.origin.y = (asize.height - rect.size.height)/2;
}
UIGraphicsBeginImageContext(asize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);
UIRectFill(CGRectMake(0, 0, asize.width, asize.height));//clear background
[image drawInRect:rect];
newimage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
return newimage;
}
2、簡單粗暴地圖片裁剪方法 裁剪出的圖片尺寸按照size的尺寸，但圖片可能會被拉伸
+ (UIImage *)thumbnailWithImage:(UIImage *)originalImage size:(CGSize)size
{
UIImage *newimage;
if (nil == image) {
newimage = nil;
}
else{
UIGraphicsBeginImageContext(asize);
[image drawInRect:CGRectMake(0, 0, asize.width, asize.height)];
newimage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
return newimage;
}
3、裁剪出的圖片尺寸按照size的尺寸，但圖片不拉伸，但多余部分會被裁減掉
+ (UIImage *)thumbnailWithImage:(UIImage *)originalImage size:(CGSize)size
{
CGSize originalsize = [originalImage size];
//原圖長寬均小於標准長寬的，不作處理返回原圖
if (originalsize.width<size.width && originalsize.height<size.height)
{
return originalImage;
}
//原圖長寬均大於標准長寬的，按比例縮小至最大適應值
else if(originalsize.width>size.width && originalsize.height>size.height)
{
CGFloat rate = 1.0;
CGFloat widthRate = originalsize.width/size.width;
CGFloat heightRate = originalsize.height/size.height;
rate = widthRate>heightRate?heightRate:widthRate;
CGImageRef imageRef = nil;
if (heightRate>widthRate)
{
imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(0, originalsize.height/2-size.height*rate/2, originalsize.width, size.height*rate));//獲取圖片整體部分
}
else
{
imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(originalsize.width/2-size.width*rate/2, 0, size.width*rate, originalsize.height));//獲取圖片整體部分
}
UIGraphicsBeginImageContext(size);//指定要繪畫圖片的大小
CGContextRef con = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(con, 0.0, size.height);
CGContextScaleCTM(con, 1.0, -1.0);
CGContextDrawImage(con, CGRectMake(0, 0, size.width, size.height), imageRef);
UIImage *standardImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CGImageRelease(imageRef);
return standardImage;
}
//原圖長寬有一項大於標准長寬的，對大於標准的那一項進行裁剪，另一項保持不變
else if(originalsize.height>size.height || originalsize.width>size.width)
{
CGImageRef imageRef = nil;
if(originalsize.height>size.height)
{
imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(0, originalsize.height/2-size.height/2, originalsize.width, size.height));//獲取圖片整體部分
}
else if (originalsize.width>size.width)
{
imageRef = CGImageCreateWithImageInRect([originalImage CGImage], CGRectMake(originalsize.width/2-size.width/2, 0, size.width, originalsize.height));//獲取圖片整體部分
}
UIGraphicsBeginImageContext(size);//指定要繪畫圖片的大小
CGContextRef con = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(con, 0.0, size.height);
CGContextScaleCTM(con, 1.0, -1.0);
CGContextDrawImage(con, CGRectMake(0, 0, size.width, size.height), imageRef);
UIImage *standardImage = UIGraphicsGetImageFromCurrentImageContext();
NSLog(@"改變后圖片的寬度為%f,圖片的高度為%f",[standardImage size].width,[standardImage size].height);
UIGraphicsEndImageContext();
CGImageRelease(imageRef);
return standardImage;
}
//原圖為標准長寬的，不做處理
else
{
return originalImage;
}
}