NSImage无法扩展

Question

我正在开发一个快速应用程序,其中我有一个方法应该将@ 2x图像重新缩放为常规图像.问题是它没有:(

为什么？

-(BOOL)createNormalImage:(NSString*)inputRetinaImagePath {

    NSImage *inputRetinaImage = [[NSImage alloc] initWithContentsOfFile:inputRetinaImagePath];



    NSSize size = NSZeroSize;
    size.width = inputRetinaImage.size.width*0.5;
    size.height = inputRetinaImage.size.height*0.5;

    [inputRetinaImage setSize:size];


    NSLog(@"%f",inputRetinaImage.size.height);


    NSBitmapImageRep *imgRep = [[inputRetinaImage representations] objectAtIndex: 0];

    NSData *data = [imgRep representationUsingType: NSPNGFileType properties: nil];

    NSString *outputFilePath = [[inputRetinaImagePath substringToIndex:inputRetinaImagePath.length - 7] stringByAppendingString:@".png"];

    NSLog([@"Normal version file path: " stringByAppendingString:outputFilePath]);
    [data writeToFile:outputFilePath atomically: NO];
    return true;
}

Answer 1

你必须非常警惕NSImage的size属性.它不一定是指bitmapRepresentation的像素尺寸,它可以参考显示的尺寸.NSImage可以具有多个位图表示,以用于不同的输出大小.

同样,更改NSImage的size属性不会改变bitmapRepresentations

因此,您需要做的是计算出您想要输出图像的大小,然后使用源NSImage中的bitmapRepresentation以该大小绘制新图像.

获得该大小取决于您获得输入图像的方式以及您对它的了解.例如,如果您确信输入图像只有一个bitmapImageRep,则可以使用此类事物(作为NSImage上的类别)

  - (NSSize) pixelSize
{
    NSBitmapImageRep* bitmap = [[self representations] objectAtIndex:0];
    return NSMakeSize(bitmap.pixelsWide,bitmap.pixelsHigh);
}

即使您有多个bitmapImageReps,第一个应该是最大的一个,如果这是您创建Retina图像的大小,它应该是您所追求的Retina大小.

当您计算出最终尺寸后,您可以制作图像:

- (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; 

}

更新

这是NSImage上像素大小获取类别的更精细版本...让我们不假设图像,它有多少imageReps,是否有任何 bitmapImageReps ...这将返回它可以找到的最大像素尺寸.如果它找不到bitMapImageRep像素尺寸,它将使用它可以获得的任何其他东西,这很可能是边界框尺寸(由eps和pdfs使用).

NSImage中+ PixelSize.h

#import <Cocoa/Cocoa.h>
#import <QuartzCore/QuartzCore.h>

@interface NSImage (PixelSize)

- (NSInteger) pixelsWide;
- (NSInteger) pixelsHigh;
- (NSSize) pixelSize;

@end

NSImage中+ PixelSize.m

#import "NSImage+PixelSize.h"

@implementation NSImage (Extensions)

- (NSInteger) pixelsWide
{
    /*
     returns the pixel width of NSImage.
     Selects the largest bitmapRep by preference
     If there is no bitmapRep returns largest size reported by any imageRep.
     */
    NSInteger result = 0;
    NSInteger bitmapResult = 0;

    for (NSImageRep* imageRep in [self representations]) {
        if ([imageRep isKindOfClass:[NSBitmapImageRep class]]) {
            if (imageRep.pixelsWide > bitmapResult)
                bitmapResult = imageRep.pixelsWide;
        } else {
            if (imageRep.pixelsWide > result)
                result = imageRep.pixelsWide;
        }
    }
    if (bitmapResult) result = bitmapResult;
    return result;

}

- (NSInteger) pixelsHigh
{
    /*
     returns the pixel height of NSImage.
     Selects the largest bitmapRep by preference
     If there is no bitmapRep returns largest size reported by any imageRep.
     */
    NSInteger result = 0;
    NSInteger bitmapResult = 0;

    for (NSImageRep* imageRep in [self representations]) {
        if ([imageRep isKindOfClass:[NSBitmapImageRep class]]) {
            if (imageRep.pixelsHigh > bitmapResult)
                bitmapResult = imageRep.pixelsHigh;
        } else {
            if (imageRep.pixelsHigh > result)
                result = imageRep.pixelsHigh;
        }
    }
    if (bitmapResult) result = bitmapResult;
    return result;
}

- (NSSize) pixelSize
{
    return NSMakeSize(self.pixelsWide,self.pixelsHigh);
}

@end

您可以#import "NSImage+PixelSize.h"在当前文件中使其可访问.

使用此图像类别和resize:方法,您可以修改您的方法:

//size.width = inputRetinaImage.size.width*0.5;
//size.height = inputRetinaImage.size.height*0.5;
size.width  = inputRetinaImage.pixelsWide*0.5;
size.height = inputRetinaImage.pixelsHigh*0.5;

//[inputRetinaImage setSize:size];
NSImage* outputImage = [self resizeImage:inputRetinaImage size:size];

//NSBitmapImageRep *imgRep = [[inputRetinaImage representations] objectAtIndex: 0];
NSBitmapImageRep *imgRep = [[outputImage representations] objectAtIndex: 0];

这应该为你解决问题(附带条件:我没有在你的代码上测试它)