UIImageresize（缩放比例）

可能重复：
调整高宽比UIImage？

下面的一段代码是完美的调整图像的大小，但问题是，它会扰乱纵横比（导致图像偏斜）。 任何指针？

// 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; } 

Answer 1

我使用这一行代码来创build一个新的UIImage这是缩放。 设置比例和方向参数来达到你想要的。 第一行代码只是抓住图像。

  // 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)]; 

Answer 2

这没关系，不是一个大问题。 你得find比例的宽度和高度

如果尺寸是2048.0 x 1360.0，必须调整到320 x 480分辨率，那么结果图像大小应该是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) 

你可以在这个网页上提交。 弧

困惑？ 好的，这里是UIImage的类别，它将为你做的事情。

 @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，以下是适当的调用。

img = [img scaleProportionalToSize：CGSizeMake（320，480）];

Answer 3

这个变化对我有用：

 // 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); 

Answer 4

这样可以将math修改为在宽度和高度上的最大尺寸，而不仅仅取决于原件的宽度和高度。

 - (UIImage *) scaleProportionalToSize: (CGSize)size { float widthRatio = size.width/self.size.width; float heightRatio = size.height/self.size.height; if(widthRatio > heightRatio) { size=CGSizeMake(self.size.width*heightRatio,self.size.height*heightRatio); } else { size=CGSizeMake(self.size.width*widthRatio,self.size.height*widthRatio); } return [self scaleToSize:size]; } 

Answer 5

尝试使bounds的大小整数。

 #include <math.h> .... if (ratio > 1) { bounds.size.width = resolution; bounds.size.height = round(bounds.size.width / ratio); } else { bounds.size.height = resolution; bounds.size.width = round(bounds.size.height * ratio); }