NSImage到NSBitmapImageRep [英] NSImage to NSBitmapImageRep

问题描述

如何将NSImage转换为NSBitmapImageRep?我有代码:

How to convert NSImage to NSBitmapImageRep? I have code:

- (NSBitmapImageRep *)bitmapImageRepresentation
{
    NSBitmapImageRep *ret = (NSBitmapImageRep *)[self representations];

    if(![ret isKindOfClass:[NSBitmapImageRep class]])
    {
        ret = nil;
        for(NSBitmapImageRep *rep in [self representations])
            if([rep isKindOfClass:[NSBitmapImageRep class]])
            {
                ret = rep;
                break;
            }
    }

    if(ret == nil)
    {
        NSSize size = [self size];

        size_t width         = size.width;
        size_t height        = size.height;
        size_t bitsPerComp   = 32;
        size_t bytesPerPixel = (bitsPerComp / CHAR_BIT) * 4;
        size_t bytesPerRow   = bytesPerPixel * width;
        size_t totalBytes    = height * bytesPerRow;

        NSMutableData *data = [NSMutableData dataWithBytesNoCopy:calloc(totalBytes, 1) length:totalBytes freeWhenDone:YES];

        CGColorSpaceRef space = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);

        CGContextRef ctx = CGBitmapContextCreate([data mutableBytes], width, height, bitsPerComp, bytesPerRow, CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB), kCGBitmapFloatComponents | kCGImageAlphaPremultipliedLast);

        if(ctx != NULL)
        {
            [NSGraphicsContext saveGraphicsState];
            [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithGraphicsPort:ctx flipped:[self isFlipped]]];

            [self drawAtPoint:NSZeroPoint fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];

            [NSGraphicsContext restoreGraphicsState];

            CGImageRef img = CGBitmapContextCreateImage(ctx);

            ret = [[NSBitmapImageRep alloc] initWithCGImage:img];
            [self addRepresentation:ret];

            CFRelease(img);
            CFRelease(space);

            CGContextRelease(ctx);
        }
    }


    return ret;
}

它可以工作，但是会导致内存泄漏.至少当我将它与ARC一起使用时.使用initWithData:[nsimagename TIFFRepresentation]不能正常工作.有些图像的表示不好.我认为这取决于图像的格式和色彩空间.还有其他方法可以实现吗?

It works, but it causes memory leaks. At least when I am using it with ARC. Using initWithData:[nsimagename TIFFRepresentation] it not working correctly. Some images`s representations are not good. I think it depends on format and colorspace of image. Is there any other ways to achieve that?

结果为 mrwalker 的建议解决方案:

Result with mrwalker suggested solution:

原始图片:

Original image:

转换为bitmapimagerep并返回图像1次:

Converted to bitmapimagerep and back to image 1 time:

转换为bitmapimagerep并返回图像3次:

Converted to bitmapimagerep and back to image 3 times:

如您所见，每次转换为NSBitmapImageRep后，图像都会变暗

As you see image gets darker every time after converting to NSBitmapImageRep

推荐答案

您可以尝试从:

- (NSBitmapImageRep *)bitmapImageRepresentation {
  int width = [self size].width;
  int height = [self size].height;

  if(width < 1 || height < 1)
      return nil;

  NSBitmapImageRep *rep = [[NSBitmapImageRep alloc]
                           initWithBitmapDataPlanes: NULL
                           pixelsWide: width
                           pixelsHigh: height
                           bitsPerSample: 8
                           samplesPerPixel: 4
                           hasAlpha: YES
                           isPlanar: NO
                           colorSpaceName: NSDeviceRGBColorSpace
                           bytesPerRow: width * 4
                           bitsPerPixel: 32];

  NSGraphicsContext *ctx = [NSGraphicsContext graphicsContextWithBitmapImageRep: rep];
  [NSGraphicsContext saveGraphicsState];
  [NSGraphicsContext setCurrentContext: ctx];  
  [self drawAtPoint: NSZeroPoint fromRect: NSZeroRect operation: NSCompositeCopy fraction: 1.0];
  [ctx flushGraphics];
  [NSGraphicsContext restoreGraphicsState];

  return [rep autorelease];
}

这篇关于NSImage到NSBitmapImageRep的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！