缩放nimage并保存

Question

我想把一张64px的图片放大到512px(即使它是模糊的或像素化的)

我用这个从NSImageView中获取图像并保存它:

NSData *customimageData = [[customIcon image] TIFFRepresentation];
    NSBitmapImageRep *customimageRep = [NSBitmapImageRep imageRepWithData:customimageData];

    customimageData = [customimageRep representationUsingType:NSPNGFileType properties:nil];

    NSString* customBundlePath = [[NSBundle mainBundle] pathForResource:@"customIcon" ofType:@"png"];
    [customimageData writeToFile:customBundlePath atomically:YES];

我试过setSize:但它仍然保存64px。

提前感谢!

Answer 1

你不能使用NSImage的size属性，因为它与图像表示的像素尺寸只有间接关系。调整像素尺寸的一个好方法是使用NSImageRep:

的drawInRect方法。

 - (BOOL)drawInRect:(NSRect)rect

在指定的矩形中绘制整个图像，并根据需要进行缩放。

这是一个图像大小调整方法(创建一个新的NSImage在你想要的像素大小)。

- (NSImage*) resizeImage:(NSImage*)sourceImage size:(NSSize)size
{
    NSRect targetFrame = NSMakeRect(0, 0, size.width, size.height);     
    NSImage* targetImage = nil;
    NSImageRep *sourceImageRep =
    [sourceImage bestRepresentationForRect:targetFrame
                                   context:nil
                                     hints:nil];
    targetImage = [[NSImage alloc] initWithSize:size];
    [targetImage lockFocus];
    [sourceImageRep drawInRect: targetFrame];
    [targetImage unlockFocus];
return targetImage; 
}

它来自我在这里给出的更详细的答案:NSImage不缩放

另一个有效的方法是NSImage方法drawInRect:fromRect:operation:fraction:respectFlipped:hints

- (void)drawInRect:(NSRect)dstSpacePortionRect 
          fromRect:(NSRect)srcSpacePortionRect 
         operation:(NSCompositingOperation)op 
          fraction:(CGFloat)requestedAlpha 
    respectFlipped:(BOOL)respectContextIsFlipped 
             hints:(NSDictionary *)hints

该方法的主要优点是hints NSDictionary，其中您可以对插值进行一些控制。当放大图像时，这可能会产生截然不同的结果。NSImageHintInterpolation是一个enum，可以接受以下五个值之一:

    enum {
       NSImageInterpolationDefault = 0,
       NSImageInterpolationNone = 1,
       NSImageInterpolationLow = 2,
       NSImageInterpolationMedium = 4,
       NSImageInterpolationHigh = 3
    };
    typedef NSUInteger NSImageInterpolation;

使用这种方法，不需要提取imageRep的中间步骤，NSImage会做正确的事情…

- (NSImage*) resizeImage:(NSImage*)sourceImage size:(NSSize)size
{
    NSRect targetFrame = NSMakeRect(0, 0, size.width, size.height);
    NSImage*  targetImage = [[NSImage alloc] initWithSize:size];
    [targetImage lockFocus];
    [sourceImage drawInRect:targetFrame
                   fromRect:NSZeroRect       //portion of source image to draw 
                  operation:NSCompositeCopy  //compositing operation
                   fraction:1.0              //alpha (transparency) value
             respectFlipped:YES              //coordinate system
                      hints:@{NSImageHintInterpolation:
     [NSNumber numberWithInt:NSImageInterpolationLow]}];
    [targetImage unlockFocus];
    return targetImage;
}