xcode – 如何从NSImage保存PNG文件(视网膜问题)正确的方法？

我试图将数组中的每个图像保存为.PNG文件(也是正确的大小,因为视网膜mac dpi问题没有按比例放大)并且似乎无法找到解决方案.在 How to save PNG file from NSImage (retina issues)没有任何解决方案似乎对我有用.我已经尝试了每一个,他们每个人仍然会在视网膜.etc中将72×72文件保存为144×144.

更具体地说,我正在寻找一个NSImage类别(是的,我在Mac环境中工作)

我试图让用户选择一个目录来保存它们并执行从数组中保存图像,如下所示：

- (IBAction)saveImages:(id)sender {
    // Prepare Images that are checked and put them in an array
    [self prepareImages];

    if ([preparedImages count] == 0) {
        NSLog(@"We have no preparedImages to save!");
        NSAlert *alert = [[NSAlert alloc] init];
        [alert setAlertStyle:NSInformationalAlertStyle];
        [alert setMessageText:NSLocalizedString(@"Error",@"Save Images Error Text")];
        [alert setInformativeText:NSLocalizedString(@"You have not selected any images to create.",@"Save Images Error Informative Text")];

        [alert beginSheetModalForWindow:self.window
                          modalDelegate:self
                        didEndSelector:@selector(testDatabaseConnectionDidEnd:returnCode:
                                                   contextInfo:)
                            contextInfo:nil];
        return;
    } else {
        NSLog(@"We have prepared %lu images.",(unsigned long)[preparedImages count]);
    }

    // Save Dialog
    // Create a File Open Dialog class.
    //NSOpenPanel* openDlg = [NSOpenPanel openPanel];
    NSSavePanel *panel = [NSSavePanel savePanel];

    // Set array of file types
    NSArray *fileTypesArray;
    fileTypesArray = [NSArray arrayWithObjects:@"jpg",@"gif",@"png",nil];

    // Enable options in the dialog.
    //[openDlg setCanChooseFiles:YES];
    //[openDlg setAllowedFileTypes:fileTypesArray];
    //[openDlg setAllowsMultipleSelection:TRUE];
    [panel setNameFieldStringValue:@"Images.png"];
    [panel setDirectoryURL:directoryPath];


    // Display the dialog box.  If the OK pressed,// process the files.
    [panel beginWithCompletionHandler:^(NSInteger result) {

        if (result == NSFileHandlingPanelOKButton) {
            NSLog(@"OK Button!");
            // create a file manager and grab the save panel's returned URL
            NSFileManager *manager = [NSFileManager defaultManager];
            directoryPath = [panel URL];
            [[self directoryLabel] setStringValue:[NSString stringWithFormat:@"%@",directoryPath]];

            // then copy a previous file to the new location

            // copy item at URL was self.myURL
            // copy images that are created from array to this path


            for (NSImage *image in preparedImages) {
#warning Fix Copy Item At URL to copy image from preparedImages array to save each one
                NSString *imageName = image.name;
                NSString *imagePath = [[directoryPath absoluteString] stringByAppendingPathComponent:imageName];

                //[manager copyItemAtURL:nil toURL:directoryPath error:nil];
                NSLog(@"Trying to write IMAGE: %@ to URL: %@",imageName,imagePath);
                //[image writePNGToURL:[NSURL URLWithString:imagePath] outputSizeInPixels:image.size error:nil];
                [self saveImage:image atPath:imagePath];
            }
            //[manager copyItemAtURL:nil toURL:directoryPath error:nil];


        }
    }];

    [preparedImages removeAllObjects];

    return;

}

一个用户试图通过使用此NSImage类别来回答他,但它不会为我生成任何文件或PNG.

@interface NSImage (SSWPNGAdditions)

- (BOOL)writePNGToURL:(NSURL*)URL outputSizeInPixels:(NSSize)outputSizePx error:(NSError*__autoreleasing*)error;

@end

@implementation NSImage (SSWPNGAdditions)

- (BOOL)writePNGToURL:(NSURL*)URL outputSizeInPixels:(NSSize)outputSizePx error:(NSError*__autoreleasing*)error
{
    BOOL result = YES;
    NSImage* scalingImage = [NSImage imageWithSize:[self size] flipped:[self isFlipped] drawingHandler:^BOOL(NSRect dstRect) {
        [self drawAtPoint:NSMakePoint(0.0,0.0) fromRect:dstRect operation:NSCompositeSourceOver fraction:1.0];
        return YES;
    }];
    NSRect proposedRect = NSMakeRect(0.0,0.0,outputSizePx.width,outputSizePx.height);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
    CGContextRef cgContext = CGBitmapContextCreate(NULL,proposedRect.size.width,proposedRect.size.height,8,4*proposedRect.size.width,colorSpace,kCGImageAlphaPremultipliedLast);
    CGColorSpaceRelease(colorSpace);
    NSGraphicsContext* context = [NSGraphicsContext graphicsContextWithGraphicsPort:cgContext flipped:NO];
    CGContextRelease(cgContext);
    CGImageRef cgImage = [scalingImage CGImageForProposedRect:&proposedRect context:context hints:nil];
    CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)(URL),kUTTypePNG,1,NULL);
    CGImageDestinationAddImage(destination,cgImage,nil);
    if(!CGImageDestinationFinalize(destination))
    {
        NSDictionary* details = @{NSLocalizedDescriptionKey:@"Error writing PNG image"};
        [details setValue:@"ran out of money" forKey:NSLocalizedDescriptionKey];
        *error = [NSError errorWithDomain:@"SSWPNGAdditionsErrorDomain" code:10 userInfo:details];
        result = NO;
    }
    CFRelease(destination);
    return result;
}

@end

NSBitmapImageRep *myRep = [myImage unscaledBitmapImageRep];

-(NSBitmapImageRep *)unscaledBitmapImageRep {

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

   [NSGraphicsContext saveGraphicsState];
   [NSGraphicsContext setCurrentContext:
            [NSGraphicsContext graphicsContextWithBitmapImageRep:rep]];

    [self drawAtPoint:NSMakePoint(0,0) 
             fromRect:NSZeroRect 
            operation:NSCompositeSourceOver 
             fraction:1.0];

    [NSGraphicsContext restoreGraphicsState];
    return rep;
}