UIImage调整大小(缩放比例)
UIImage调整大小(缩放比例)
提问于 2010-04-15 21:43:07
可能重复：
Resize UIImage with aspect ratio?
下面的代码完美地调整了图像的大小，但问题是它弄乱了纵横比(导致图像倾斜)。有什么建议吗？
// Change image resolution (auto-resize to fit)
+ (UIImage *)scaleImage:(UIImage*)image toResolution:(int)resolution {
CGImageRef imgRef = [image CGImage];
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGRect bounds = CGRectMake(0, 0, width, height);
//if already at the minimum resolution, return the orginal image, otherwise scale
if (width <= resolution && height <= resolution) {
return image;
} else {
CGFloat ratio = width/height;
if (ratio > 1) {
bounds.size.width = resolution;
bounds.size.height = bounds.size.width / ratio;
} else {
bounds.size.height = resolution;
bounds.size.width = bounds.size.height * ratio;
}
}
UIGraphicsBeginImageContext(bounds.size);
[image drawInRect:CGRectMake(0.0, 0.0, bounds.size.width, bounds.size.height)];
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return imageCopy;
}回答 5
Stack Overflow用户
回答已采纳
发布于 2010-04-16 15:53:28
这个改变对我很有效：
// The size returned by CGImageGetWidth(imgRef) & CGImageGetHeight(imgRef) is incorrect as it doesn't respect the image orientation!
// CGImageRef imgRef = [image CGImage];
// CGFloat width = CGImageGetWidth(imgRef);
// CGFloat height = CGImageGetHeight(imgRef);
//
// This returns the actual width and height of the photo (and hence solves the problem
CGFloat width = image.size.width;
CGFloat height = image.size.height;
CGRect bounds = CGRectMake(0, 0, width, height);Stack Overflow用户
发布于 2010-09-10 02:02:46
我使用这一行代码创建了一个新的可缩放的UIImage。设置缩放和方向参数以实现所需的效果。第一行代码只是抓取图像。
// grab the original image
UIImage *originalImage = [UIImage imageNamed:@"myImage.png"];
// scaling set to 2.0 makes the image 1/2 the size.
UIImage *scaledImage =
[UIImage imageWithCGImage:[originalImage CGImage]
scale:(originalImage.scale * 2.0)
orientation:(originalImage.imageOrientation)];Stack Overflow用户
发布于 2010-12-14 21:04:28
没关系，这不是什么大问题。问题是你得找出宽度和高度的比例
例如，如果大小为2048.0 x 1360.0，则必须将大小调整为320 x 480分辨率，则生成的图像大小应为722.0 x 480.0
here is the formulae to do that . if w,h is original and x,y are resulting image.
w/h=x/y
=>
x=(w/h)*y;
submitting w=2048,h=1360,y=480 => x=722.0 ( here width>height. if height>width then consider x to be 320 and calculate y)您可以在此网页中提交。ARC
迷惑了？好的，这是UIImage的分类，它将为你做这件事。
@interface UIImage (UIImageFunctions)
- (UIImage *) scaleToSize: (CGSize)size;
- (UIImage *) scaleProportionalToSize: (CGSize)size;
@end
@implementation UIImage (UIImageFunctions)
- (UIImage *) scaleToSize: (CGSize)size
{
// Scalling selected image to targeted size
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, size.width, size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
CGContextClearRect(context, CGRectMake(0, 0, size.width, size.height));
if(self.imageOrientation == UIImageOrientationRight)
{
CGContextRotateCTM(context, -M_PI_2);
CGContextTranslateCTM(context, -size.height, 0.0f);
CGContextDrawImage(context, CGRectMake(0, 0, size.height, size.width), self.CGImage);
}
else
CGContextDrawImage(context, CGRectMake(0, 0, size.width, size.height), self.CGImage);
CGImageRef scaledImage=CGBitmapContextCreateImage(context);
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);
UIImage *image = [UIImage imageWithCGImage: scaledImage];
CGImageRelease(scaledImage);
return image;
}
- (UIImage *) scaleProportionalToSize: (CGSize)size1
{
if(self.size.width>self.size.height)
{
NSLog(@"LandScape");
size1=CGSizeMake((self.size.width/self.size.height)*size1.height,size1.height);
}
else
{
NSLog(@"Potrait");
size1=CGSizeMake(size1.width,(self.size.height/self.size.width)*size1.width);
}
return [self scaleToSize:size1];
}
@end--如果img是UIImage实例，则以下是相应的调用。
img=img scaleProportionalToSize:CGSizeMake(320,480)
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/2645768
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