如何调整NSImage的大小

时间:2012-08-14 09:15:49

标签: objective-c macos jpeg nsimage

我的NSBitmapImageRep大小为W x H。我创建NSImage并执行addRepresentation:。然后我需要调整NSImage的大小。我尝试了setSize方法,但它不起作用。我该怎么办?

10 个答案:

答案 0 :(得分:35)

修改 由于这个答案仍然是公认的答案,但是在没有Retina屏幕的情况下编写,我将直接链接到更好的解决方案:Objective-C Swift 4


因为Paresh的方法完全正确但从10.8开始不推荐使用,我将在下面发布10.8代码。所有这些都归功于Paresh的答案。

- (NSImage *)imageResize:(NSImage*)anImage newSize:(NSSize)newSize {
    NSImage *sourceImage = anImage;
    [sourceImage setScalesWhenResized:YES];

    // Report an error if the source isn't a valid image
    if (![sourceImage isValid]){
        NSLog(@"Invalid Image");
    } else {
        NSImage *smallImage = [[NSImage alloc] initWithSize: newSize];
        [smallImage lockFocus];
        [sourceImage setSize: newSize];
        [[NSGraphicsContext currentContext] setImageInterpolation:NSImageInterpolationHigh];
        [sourceImage drawAtPoint:NSZeroPoint fromRect:CGRectMake(0, 0, newSize.width, newSize.height) operation:NSCompositeCopy fraction:1.0];
        [smallImage unlockFocus];
        return smallImage;
    }
    return nil;
}

答案 1 :(得分:26)

Thomas Johannesmeyer使用lockFocus的答案不适用于您在Retina / HiDPI屏幕上的意图:它会在屏幕的原始比例中调整为所需的,而不是像素

  • 如果您要调整屏幕的显示,请使用that method
  • 如果您正在调整具有精​​确像素尺寸的文件的大小,则在Retina(2x DPI)屏幕上运行时,它将是两倍大。

此方法从各种答案(包括this related question中的一些答案拼凑而成)调整为指定的像素尺寸,与当前屏幕DPI无关:

+ (NSImage *)resizedImage:(NSImage *)sourceImage toPixelDimensions:(NSSize)newSize
{
    if (! sourceImage.isValid) return nil;

    NSBitmapImageRep *rep = [[NSBitmapImageRep alloc]
              initWithBitmapDataPlanes:NULL
                            pixelsWide:newSize.width
                            pixelsHigh:newSize.height
                         bitsPerSample:8
                       samplesPerPixel:4
                              hasAlpha:YES
                              isPlanar:NO
                        colorSpaceName:NSCalibratedRGBColorSpace
                           bytesPerRow:0
                          bitsPerPixel:0];
    rep.size = newSize;

    [NSGraphicsContext saveGraphicsState];
    [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithBitmapImageRep:rep]];
    [sourceImage drawInRect:NSMakeRect(0, 0, newSize.width, newSize.height) fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];
    [NSGraphicsContext restoreGraphicsState];

    NSImage *newImage = [[NSImage alloc] initWithSize:newSize];
    [newImage addRepresentation:rep];
    return newImage;
}

答案 2 :(得分:16)

编辑您可以使用以下功能调整图片大小:

- (NSImage *)imageResize:(NSImage*)anImage
         newSize:(NSSize)newSize 
{
 NSImage *sourceImage = anImage;
 [sourceImage setScalesWhenResized:YES];

 // Report an error if the source isn't a valid image
 if (![sourceImage isValid])
 {
    NSLog(@"Invalid Image");
 } else
 {
    NSImage *smallImage = [[[NSImage alloc] initWithSize: newSize] autorelease];
    [smallImage lockFocus];
    [sourceImage setSize: newSize];
    [[NSGraphicsContext currentContext] setImageInterpolation:NSImageInterpolationHigh];
    [sourceImage compositeToPoint:NSZeroPoint operation:NSCompositeCopy];
    [smallImage unlockFocus];
    return smallImage;
 }
 return nil;
}

其次是这样的:

NSData *imageData = [yourImg  TIFFRepresentation]; // converting img into data
NSBitmapImageRep *imageRep = [NSBitmapImageRep imageRepWithData:imageData]; // converting into BitmapImageRep 
NSDictionary *imageProps = [NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:0.9] forKey:NSImageCompressionFactor]; // any number betwwen 0 to 1
imageData = [imageRep representationUsingType:NSJPEGFileType properties:imageProps]; // use NSPNGFileType if needed
NSImage *resizedImage = [[NSImage alloc] initWithData:imageData]; // image created from data

答案 3 :(得分:14)

实际上无需来修改size等任何源图像参数。以下代码片段已经在Swift中,但我认为您可以从中推断出Objective-C版本:

func resized(to: CGSize) -> NSImage {
    let img = NSImage(size: to)

    img.lockFocus()
    defer {
        img.unlockFocus()
    }

    if let ctx = NSGraphicsContext.current {
        ctx.imageInterpolation = .high
        draw(in: NSRect(origin: .zero, size: to),
             from: NSRect(origin: .zero, size: size),
             operation: .copy,
             fraction: 1)
    }

    return img
}

答案 4 :(得分:9)

Swift 4:

撰写的

@Marco's answer

">click here</a>...),

答案 5 :(得分:4)

这里是Thomas Johannesmeyer's answer的Swift 4版本:

var oModel = this.getView().getModel("myJsonModel");
this.getView().getModel().read("/Meetups", {
    success: function(oData) {
        oModel.setData(oData);
    }
});

Swift 4版Marco's answer

func resize(image: NSImage, w: Int, h: Int) -> NSImage {
    var destSize = NSMakeSize(CGFloat(w), CGFloat(h))
    var newImage = NSImage(size: destSize)
    newImage.lockFocus()
    image.draw(in: NSMakeRect(0, 0, destSize.width, destSize.height), from: NSMakeRect(0, 0, image.size.width, image.size.height), operation: NSCompositingOperation.sourceOver, fraction: CGFloat(1))
    newImage.unlockFocus()
    newImage.size = destSize
    return NSImage(data: newImage.tiffRepresentation!)!
}

答案 6 :(得分:3)

完成Swift 3的答案(修改自@Erik Aigner above):

extension NSImage {
    func resizeImage(width: CGFloat, _ height: CGFloat) -> NSImage {
        let img = NSImage(size: CGSize(width:width, height:height))

        img.lockFocus()
        let ctx = NSGraphicsContext.current()
        ctx?.imageInterpolation = .high
        self.draw(in: NSMakeRect(0, 0, width, height), from: NSMakeRect(0, 0, size.width, size.height), operation: .copy, fraction: 1)
        img.unlockFocus()

        return img
    }
}

答案 7 :(得分:2)

2020年| SWIFT 4和5:

用法:

let resizedImg = someImage.resizedCopy(w: 500.0, h:500.0)
let scaledImg = someImage.scaledCopy( sizeOfLargerSide: 1000.0)

//and bonus:
scaledImg.writePNG(toURL: someUrl )

代码:

extension NSImage {
    func scaledCopy( sizeOfLargerSide: CGFloat) ->  NSImage {
        var newW: CGFloat
        var newH: CGFloat
        var scaleFactor: CGFloat
        
        if ( self.size.width > self.size.height) {
            scaleFactor = self.size.width / sizeOfLargerSide
            newW = sizeOfLargerSide
            newH = self.size.height / scaleFactor
        }
        else{
            scaleFactor = self.size.height / sizeOfLargerSide
            newH = sizeOfLargerSide
            newW = self.size.width / scaleFactor
        }
        
        return resizedCopy(w: newW, h: newH)
    }
    
    
    func resizedCopy( w: CGFloat, h: CGFloat) -> NSImage {
        let destSize = NSMakeSize(w, h)
        let newImage = NSImage(size: destSize)
        
        newImage.lockFocus()
        
        self.draw(in: NSRect(origin: .zero, size: destSize),
                  from: NSRect(origin: .zero, size: self.size),
                  operation: .copy,
                  fraction: CGFloat(1)
        )
        
        newImage.unlockFocus()
        
        guard let data = newImage.tiffRepresentation,
              let result = NSImage(data: data)
        else { return NSImage() }
        
        return result
    }
    
    public func writePNG(toURL url: URL) {
        guard let data = tiffRepresentation,
              let rep = NSBitmapImageRep(data: data),
              let imgData = rep.representation(using: .png, properties: [.compressionFactor : NSNumber(floatLiteral: 1.0)]) else {

            Swift.print("\(self) Error Function '\(#function)' Line: \(#line) No tiff rep found for image writing to \(url)")
            return
        }

        do {
            try imgData.write(to: url)
        }catch let error {
            Swift.print("\(self) Error Function '\(#function)' Line: \(#line) \(error.localizedDescription)")
        }
    }
}

答案 8 :(得分:0)

这是一个保持图像的Swift 3版本比例,只需将minimumSize设置为您想要的最小高度或宽度:

func imageResized(image: NSImage) -> NSImage {
    let ratio = image.size.height / image.size.width

    let width: CGFloat
    let height: CGFloat
    // We keep ratio of image
    if ratio > 1 {
        width = minimumSize
        height = minimumSize * ratio
    } else {
        width = minimumSize
        height = minimumSize * (1 / ratio)
    }
    let destSize = NSSize(width: width, height: height)

    let newImage = NSImage(size: destSize)
    newImage.lockFocus()
    image.draw(in: NSRect(x: 0, y: 0, width: destSize.width, height: destSize.height), from: NSRect(x: 0, y: 0, width: image.size.width, height: image.size.height), operation: .sourceOver, fraction: 1.0)
    newImage.unlockFocus()
    newImage.size = destSize
    return NSImage(data: newImage.tiffRepresentation!)!
}

答案 9 :(得分:0)

仅用于缩放NSBitmapImageRep

static NSBitmapImageRep *i_scale_bitmap(const NSBitmapImageRep *bitmap, const uint32_t width, const uint32_t height)
{
    NSBitmapImageRep *new_bitmap = NULL;
    CGImageRef dest_image = NULL;
    CGColorSpaceRef space = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
    CGContextRef context = CGBitmapContextCreate(NULL, (size_t)width, (size_t)height, PARAM(bitsPerComponent, 8), PARAM(bytesPerRow, (size_t)(width * 4)), space, kCGImageAlphaPremultipliedLast);
    CGImageRef src_image = [bitmap CGImage];
    CGRect rect = CGRectMake((CGFloat)0.f, (CGFloat)0.f, (CGFloat)width, (CGFloat)height);
    CGContextDrawImage(context, rect, src_image);
    dest_image = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGColorSpaceRelease(space);
    new_bitmap = [[NSBitmapImageRep alloc] initWithCGImage:dest_image];
    CGImageRelease(dest_image);
    return new_bitmap;
}

并用于基于NSBitmapImageRep缩放NSImage

ImageImp *imgimp_create_scaled(const ImageImp *image, const uint32_t new_width, const uint32_t new_height)
{
    NSImage *src_image = (NSImage*)image;
    NSBitmapImageRep *src_bitmap, *dest_bitmap;
    NSImage *scaled_image = nil;
    cassert_no_null(src_image);
    cassert([[src_image representations] count] == 1);
    cassert([[[src_image representations] objectAtIndex:0] isKindOfClass:[NSBitmapImageRep class]]);
    src_bitmap = (NSBitmapImageRep*)[[(NSImage*)image representations] objectAtIndex:0];
    cassert_no_null(src_bitmap);
    dest_bitmap = i_scale_bitmap(src_bitmap, new_width, new_height);
    scaled_image = [[NSImage alloc] initWithSize:NSMakeSize((CGFloat)new_width, (CGFloat)new_height)];
    [scaled_image addRepresentation:dest_bitmap];
    cassert([scaled_image retainCount] == 1);
    [dest_bitmap release];
    return (ImageImp*)scaled_image;
}

直接在NSImage上绘制([NSImage lockFocus]等)将创建NSCGImageSnapshotRep而不是NSBitmapImageRep。