我已经摆弄这个问题几乎有好几天了，即使我感觉自己总是接近启示的边缘，但我仍然无法实现我的目标。
在设计的概念阶段，我认为从iPhone的相机或库中获取图像并将其缩小到指定的高度（完全使用代码中 UIImageView 的 Aspect Fill 选项的等效函数），然后裁剪未适应传递的 CGRect 中的任何部分，将是一个微不足道的事情。
从相机或库获得原始图像很简单。但让我感到震惊的是，另外两个步骤证明是多么困难。
附加的图像显示了我要实现的内容。请有人帮我吗？迄今为止找到的每个代码示例似乎都会破坏图像，上下颠倒，看起来很糟糕，绘制出界，或者根本不能正确地工作。
我也需要同样的功能 - 在我的情况下，是挑选适合缩放后尺寸的维度，然后裁剪两端以适应宽度。(我在横向模式下工作，所以可能没有注意到纵向模式下的任何缺陷。) 这是我的代码 - 它是UIImage类别的一部分。在我的代码中，目标大小始终设置为设备的全屏大小。
@implementation UIImage (Extras)
#pragma mark -
#pragma mark Scale and crop image
- (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize
{
UIImage *sourceImage = self;
UIImage *newImage = nil;
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;
}
}
}
UIGraphicsBeginImageContext(targetSize); // this will crop
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = thumbnailPoint;
thumbnailRect.size.width = scaledWidth;
thumbnailRect.size.height = scaledHeight;
[sourceImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();
if(newImage == nil)
{
NSLog(@"could not scale image");
}
//pop the context to get back to the default
UIGraphicsEndImageContext();
return newImage;
}
一篇较旧的帖子包含了调整 UIImage 尺寸的方法代码。相关部分如下：
+ (UIImage*)imageWithImage:(UIImage*)image
scaledToSize:(CGSize)newSize;
{
UIGraphicsBeginImageContext( newSize );
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
就裁剪而言，我认为如果你改变方法，使用不同于上下文的大小进行缩放，则结果图像应该被剪切到上下文的边界。
originalImage的正确方向。谢谢。 - BrendenUIGraphicsBeginImageContextWithOptions(newSize, 1.0f, 0.0f);。（解释见此链接：https://dev59.com/s2855IYBdhLWcg3wcz_y） - johngraham+ (UIImage *)scaleImage:(UIImage *)image toSize:(CGSize)targetSize {
//If scaleFactor is not touched, no scaling will occur
CGFloat scaleFactor = 1.0;
//Deciding which factor to use to scale the image (factor = targetSize / imageSize)
if (image.size.width > targetSize.width || image.size.height > targetSize.height)
if (!((scaleFactor = (targetSize.width / image.size.width)) > (targetSize.height / image.size.height))) //scale to fit width, or
scaleFactor = targetSize.height / image.size.height; // scale to fit heigth.
UIGraphicsBeginImageContext(targetSize);
//Creating the rect where the scaled image is drawn in
CGRect rect = CGRectMake((targetSize.width - image.size.width * scaleFactor) / 2,
(targetSize.height - image.size.height * scaleFactor) / 2,
image.size.width * scaleFactor, image.size.height * scaleFactor);
//Draw the image into the rect
[image drawInRect:rect];
//Saving the image, ending image context
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}
我建议这个。她不是美女吗？ ;)
有一个很棒的代码与调整图像大小和多个其他操作相关。我在尝试解决如何调整图片大小时发现了这个代码...
http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/这是Jane Sales的Swift版本答案。干杯！
public func resizeImage(image: UIImage, size: CGSize) -> UIImage? {
var returnImage: UIImage?
var scaleFactor: CGFloat = 1.0
var scaledWidth = size.width
var scaledHeight = size.height
var thumbnailPoint = CGPointMake(0, 0)
if !CGSizeEqualToSize(image.size, size) {
let widthFactor = size.width / image.size.width
let heightFactor = size.height / image.size.height
if widthFactor > heightFactor {
scaleFactor = widthFactor
} else {
scaleFactor = heightFactor
}
scaledWidth = image.size.width * scaleFactor
scaledHeight = image.size.height * scaleFactor
if widthFactor > heightFactor {
thumbnailPoint.y = (size.height - scaledHeight) * 0.5
} else if widthFactor < heightFactor {
thumbnailPoint.x = (size.width - scaledWidth) * 0.5
}
}
UIGraphicsBeginImageContextWithOptions(size, true, 0)
var thumbnailRect = CGRectZero
thumbnailRect.origin = thumbnailPoint
thumbnailRect.size.width = scaledWidth
thumbnailRect.size.height = scaledHeight
image.drawInRect(thumbnailRect)
returnImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return returnImage
}
给你，这个非常完美;-)
编辑：请看下面的评论 - "与某些图像不兼容，在CGContextSetInterpolationQuality: invalid context 0x0错误时失败"
// Resizes the image according to the given content mode, taking into account the image's orientation
- (UIImage *)resizedImageWithContentMode:(UIViewContentMode)contentMode imageToScale:(UIImage*)imageToScale bounds:(CGSize)bounds interpolationQuality:(CGInterpolationQuality)quality {
//Get the size we want to scale it to
CGFloat horizontalRatio = bounds.width / imageToScale.size.width;
CGFloat verticalRatio = bounds.height / imageToScale.size.height;
CGFloat ratio;
switch (contentMode) {
case UIViewContentModeScaleAspectFill:
ratio = MAX(horizontalRatio, verticalRatio);
break;
case UIViewContentModeScaleAspectFit:
ratio = MIN(horizontalRatio, verticalRatio);
break;
default:
[NSException raise:NSInvalidArgumentException format:@"Unsupported content mode: %d", contentMode];
}
//...and here it is
CGSize newSize = CGSizeMake(imageToScale.size.width * ratio, imageToScale.size.height * ratio);
//start scaling it
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
CGImageRef imageRef = imageToScale.CGImage;
CGContextRef bitmap = CGBitmapContextCreate(NULL,
newRect.size.width,
newRect.size.height,
CGImageGetBitsPerComponent(imageRef),
0,
CGImageGetColorSpace(imageRef),
CGImageGetBitmapInfo(imageRef));
CGContextSetInterpolationQuality(bitmap, quality);
// Draw into the context; this scales the image
CGContextDrawImage(bitmap, newRect, imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
// Clean up
CGContextRelease(bitmap);
CGImageRelease(newImageRef);
return newImage;
}
我发现Evgenii Kanvets发布的Swift 3版本不能均匀缩放图像。
这是我基于Swift 4的函数版本，它不会扭曲图像：
static func resizedCroppedImage(image: UIImage, newSize:CGSize) -> UIImage? {
// This function returns a newImage, based on image
// - image is scaled uniformaly to fit into a rect of size newSize
// - if the newSize rect is of a different aspect ratio from the source image
// the new image is cropped to be in the center of the source image
// (the excess source image is removed)
var ratio: CGFloat = 0
var delta: CGFloat = 0
var drawRect = CGRect()
if newSize.width > newSize.height {
ratio = newSize.width / image.size.width
delta = (ratio * image.size.height) - newSize.height
drawRect = CGRect(x: 0, y: -delta / 2, width: newSize.width, height: newSize.height + delta)
} else {
ratio = newSize.height / image.size.height
delta = (ratio * image.size.width) - newSize.width
drawRect = CGRect(x: -delta / 2, y: 0, width: newSize.width + delta, height: newSize.height)
}
UIGraphicsBeginImageContextWithOptions(newSize, true, 0.0)
image.draw(in: drawRect)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
UIGraphicsBeginImageContextWithOptions中将缩放设置为1.0，但其他的都完美地工作了。谢谢！ - maxmzdif aspectRatio < newAspectRatio而不是检查if newSize.width > newSize.height。我将更新发布到@ChrisCapener的代码中，作为单独的答案。 - P. SternscrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0,0.0,ScreenWidth,ScreenHeigth)];
[scrollView setBackgroundColor:[UIColor blackColor]];
[scrollView setDelegate:self];
[scrollView setShowsHorizontalScrollIndicator:NO];
[scrollView setShowsVerticalScrollIndicator:NO];
[scrollView setMaximumZoomScale:2.0];
image=[image scaleToSize:CGSizeMake(ScreenWidth, ScreenHeigth)];
imageView = [[UIImageView alloc] initWithImage:image];
UIImageView* imageViewBk = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"background.png"]];
[self.view addSubview:imageViewBk];
CGRect rect;
rect.origin.x=0;
rect.origin.y=0;
rect.size.width = image.size.width;
rect.size.height = image.size.height;
[imageView setFrame:rect];
[scrollView setContentSize:[imageView frame].size];
[scrollView setMinimumZoomScale:[scrollView frame].size.width / [imageView frame].size.width];
[scrollView setZoomScale:[scrollView minimumZoomScale]];
[scrollView addSubview:imageView];
[[self view] addSubview:scrollView];
float zoomScale = 1.0 / [scrollView zoomScale];
CGRect rect;
rect.origin.x = [scrollView contentOffset].x * zoomScale;
rect.origin.y = [scrollView contentOffset].y * zoomScale;
rect.size.width = [scrollView bounds].size.width * zoomScale;
rect.size.height = [scrollView bounds].size.height * zoomScale;
CGImageRef cr = CGImageCreateWithImageInRect([[imageView image] CGImage], rect);
UIImage *cropped = [UIImage imageWithCGImage:cr];
CGImageRelease(cr);
我修改了Brad Larson的代码，它将会在给定的矩形中填充图像。
-(UIImage*) scaleAndCropToSize:(CGSize)newSize;
{
float ratio = self.size.width / self.size.height;
UIGraphicsBeginImageContext(newSize);
if (ratio > 1) {
CGFloat newWidth = ratio * newSize.width;
CGFloat newHeight = newSize.height;
CGFloat leftMargin = (newWidth - newHeight) / 2;
[self drawInRect:CGRectMake(-leftMargin, 0, newWidth, newHeight)];
}
else {
CGFloat newWidth = newSize.width;
CGFloat newHeight = newSize.height / ratio;
CGFloat topMargin = (newHeight - newWidth) / 2;
[self drawInRect:CGRectMake(0, -topMargin, newSize.width, newSize.height/ratio)];
}
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Xamarin.iOS 版本的如何调整大小并裁剪 UIImage（Aspect Fill）的接受答案代码如下：
public static UIImage ScaleAndCropImage(UIImage sourceImage, SizeF targetSize)
{
var imageSize = sourceImage.Size;
UIImage newImage = null;
var width = imageSize.Width;
var height = imageSize.Height;
var targetWidth = targetSize.Width;
var targetHeight = targetSize.Height;
var scaleFactor = 0.0f;
var scaledWidth = targetWidth;
var scaledHeight = targetHeight;
var thumbnailPoint = PointF.Empty;
if (imageSize != targetSize)
{
var widthFactor = targetWidth / width;
var 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) * 0.5f;
}
else
{
if (widthFactor < heightFactor)
{
thumbnailPoint.X = (targetWidth - scaledWidth) * 0.5f;
}
}
}
UIGraphics.BeginImageContextWithOptions(targetSize, false, 0.0f);
var thumbnailRect = new RectangleF(thumbnailPoint, new SizeF(scaledWidth, scaledHeight));
sourceImage.Draw(thumbnailRect);
newImage = UIGraphics.GetImageFromCurrentImageContext();
if (newImage == null)
{
Console.WriteLine("could not scale image");
}
//pop the context to get back to the default
UIGraphics.EndImageContext();
return newImage;
}