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REBOL [ Title: "PNG Examiner" Date: 25-Nov-2001 Version: 0.0.2 File: %png.r Home: Author: "oldes" Purpose: {Basic PNG (Portable Network Graphics) parser which can show all informations from standard chunks in the file. } History: [ 0.0.2 [25-Nov-2001 "Fixed small bug in parsing textual data." "oldes"] 0.0.1 [31-Aug-2000 "Initial version" "oldes"] ] Email: %oliva--david--seznam--cz library: [ level: 'intermediate platform: none type: 'tool domain: 'file-handling tested-under: none support: none license: none see-also: none ] ] if empty? png-file: to-file ask "PNG file: " [png-file: %/d/test.png] png-bin: read/binary png-file png: make object! [ header: none Color-type: none Color-types: [ 0 "grayscale, without alpha" 2 "truecolor, without alpha" 3 "indexed color" 4 "grayscale, with alpha" 6 "truecolor, with alpha" ] chunks: make block! 6 chunk: make object! [ length: none type: none data: none CRC: none ] chunk-bytes: [ "IHDR" [4 4 1 1 1 1 1] "PLTE" [] "IDAT" [] "IEND" [] "cHRM" [4 4 4 4 4 4 4 4] "gAMA" [4] "sBIT" [] "bKGD" [] "hIST" [] "tRNS" [] "pHYs" [4 4 1] "tIME" [2 1 1 1 1 1] "tEXt" [] "zTXt" [] ] ] print ["PNG size:" length? png-bin "bytes"] png/header: copy/part png-bin 8 png-bin: skip png-bin 8 if png/header <> #{89504E470D0A1A0A} [print "Illegal PNG header!" halt] ;help functions: getpart: func[bytes /local tmp][ tmp: copy/part png-bin bytes png-bin: skip png-bin bytes tmp ] slice-bin: func [bin bytes /integers /local tmp b][ tmp: make block! length? bytes forall bytes [ b: copy/part bin bytes/1 append tmp either integers [to-integer b][b] bin: skip bin bytes/1 ] tmp ] extract-data: func[type][ png/chunk/data: slice-bin/integers png/chunk/data select png/chunk-bytes type ] ;end of help functions prin "Searching for chunks... " while [not tail? png-bin][ png/chunk/length: to-integer getpart 4 ;length png/chunk/type: to-string getpart 4 ;type png/chunk/data: getpart png/chunk/length ;data png/chunk/CRC: getpart 4 ;CRC repend png/chunks [png/chunk/length png/chunk/CRC png/chunk/type] switch png/chunk/type [ "IHDR" [extract-data "IHDR"] ;Image header "sBIT" [] ;Significant bits "pHYs" [extract-data "pHYs"] ;Physical pixel dimensions "cHRM" [extract-data "cHRM"] ;Primary chromaticities and white point "gAMA" [extract-data "gAMA"] ;Image gamma "hIST" [] ;Image histogram "tEXt" [;Textual data parse/all png/chunk/data [copy k to #"^@" 1 skip copy d to end] png/chunk/data: reduce [k d] ] "tIME" [;Image last-modification time extract-data "tIME" png/chunk/data: to-date rejoin [png/chunk/data/3 "-" png/chunk/data/2 "-" png/chunk/data/1 "/" png/chunk/data/4 ":" png/chunk/data/5 ":" png/chunk/data/6] ] "tRNS" [];Transparency "zTXt" [;Compressed textual data parse png/chunk/data [copy k to #"^@" 1 skip copy cm 1 skip copy d to end] png/chunk/data: reduce [k cm d] ] ] repend/only png/chunks png/chunk/data ] print ["found" (length? png/chunks) / 4 "chunks."] ;show results: print "-------------------------------------------" foreach [length crc type data] png/chunks [ switch/default type [ "IHDR" [;Image header print ["Width_______________" data/1 "pixels"] print ["Height______________" data/2 "pixels"] print ["Bit depth___________" data/3] print ["Color type__________" data/4 "(" select png/color-types data/4 ")"] print ["Compression method__" data/5] print ["Filter method_______" data/6] print ["Interlace method____" data/7] ] "PLTE" [print ["Palette: " mold data]] "IDAT" [print ["Image data:" length? data "B"] ] "IEND" [print "Image trailer - EOF"] ;Ancillary chunks "bKGD" [print ["Background color:" mold data]] "cHRM" [ print "Primary chromaticities and white point:" print [" White Point x__" data/1] print [" White Point y__" data/2] print [" Red x__________" data/3] print [" Red y__________" data/4] print [" Green x________" data/5] print [" Green y________" data/6] print [" Blue x_________" data/7] print [" Blue y_________" data/8] ] "gAMA" [print ["Image gamma:__" data]] "hIST" [print ["Image histogram:" data]] "pHYs" [;Physical pixel dimensions Print ["Pixels per unit, X axis: " data/1] Print ["Pixels per unit, Y axis: " data/2] Print ["Unit specifier: " data/3 "(" pick ["unknown" "meter"] (data/3 + 1) ")"] ] "sBIT" [print ["Significant bits:" data]] "tEXt" [print [data/1 ":" data/2]] "tRNS" [print ["Transparency:____" data]] "zTXt" [ print "Compressed textual data:" print [" " data/1 data/2 data/3] ] ][ either find png/chunk-bytes type [ prin [type " "] probe data ][ print ["Nonstandard" either (to-integer type/2) > 88 ["private"]["public"] "chunk:" type] ] ] ]
halt ;; to terminate script if DO'ne from webpage
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