Grammar for the popular PNG image file format Defines the default values. Each pixel is a grayscale sample. Each pixel is an R,G,B triple. Each pixel is a palette index; a PLTE chunk must appear. Each pixel is a grayscale sample, followed by an alpha sample. Each pixel is an R,G,B triple, followed by an alpha sample. deflate/inflate compression with a sliding window of at most 32768 bytes zlib datastream with deflate compression Uncompressed text Compressed text zlib datastream with deflate compression zlib datastream with deflate compression Applications that need device-independent specification of colors in a PNG file can use the cHRM chunk to specify the 1931 CIE x,y chromaticities of the red, green, and blue primaries used in the image, and the referenced white point