When creating image files via CGImageDestination if found something weird. I'm setting the DPIHeight and DPIWidth fields in the meta info to 72. When outputting as PNG format there are some programs that will show the image resolution as 72.009 DPI, whereas TIFF and JPEG for example would display as 72. Turns out that this is neither a problem of CGImageDestination, libpng nor any specific viewer app. The problem is in the PNG specification. Consider the following output meta info I created with Pixelmator: { ColorModel = RGB; DPIHeight = 72; DPIWidth = 72; Depth = 8; HasAlpha = 1; Orientation = 1; PixelHeight = 1024; PixelWidth = 1024; ProfileName = "sRGB IEC61966-2.1"; "{Exif}" = { ColorSpace = 1; PixelXDimension = 1024; PixelYDimension = 1024; }; "{PNG}" = { InterlaceType = 0; Software = "Pixelmator 2.1.4"; XPixelsPerMeter = 2835; YPixelsPerMeter = 2835; }; More