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

概述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 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

解决方法 我在原始 thread中提供的答案也遇到了麻烦.进一步的阅读使得Erica Sadun在 post上找到了与没有视网膜显示器的视网膜显示器调试代码有关的问题.她创建了所需大小的位图,然后将当前绘图上下文(基于显示/视网膜受影响)替换为与新位图关联的通用图形.然后,她将原始图像渲染到位图中(使用通用图形上下文).

我拿了她的代码并在NSImage上做了一个快速的类别,它似乎为我做了这个工作.打电话后

NSBitmAPImageRep *myRep = [myImage unscaledBitmAPImageRep];

你应该有一个正确(原始)尺寸的位图,无论你开始使用什么类型的物理显示.从这一点开始,您可以在未缩放的位图上调用representationUsingType：属性,以获得您要写出的任何格式.

这是我的类别(标题省略).注意 – 您可能需要公开位图初始化程序的颜色空间部分.这是适用于我的特定情况的价值.

-(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;}

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