; Copyright (c) 2003 RT Happe <rthappe at web de>
; See the file COPYING distributed with the Scheme Untergrund Library
; See the file README for documentation.
;;; since there is no pre-fab lazy-list facility for s48/scsh but a
;;; draft srfi, I don't use what's not there and don't set up a
;;; full-fledged facility myself. An ad hoc hack shall do for now.
(define (inport->byte-stream in)
(delay (let ((b (read-byte in)))
(if (eof-object? b) '()
(cons b (inport->byte-stream in))))))
(define (byte-vector->byte-stream bv)
(let ((max (- (byte-vector-length bv) 1)))
(let loop ((min 0))
(if (< min max)
(delay (cons (byte-vector-ref bv min)
(loop (+ min 1))))
(delay '())))))
(define (segment-byte-stream bs start end)
(assert (<= start end) segment-byte-stream)
(let* ((bv (make-byte-vector (- end start) 0)))
(let loop ((i 0) (bs bs))
(cond ((< i start)
(let ((bytes (force bs)))
(if (null? bytes)
(values (byte-vector) bs)
(loop (+ i 1) (cdr bytes)))))
((= i end) (values bv bs))
;; start <= i < end
(else (let ((bytes (force bs)))
(if (null? bytes)
(values (subsequence bv 0 (- i start)) bs)
(begin
(byte-vector-set! bv (- i start) (car bytes))
(loop (+ i 1) (cdr bytes)))))))
)))
;; bytes : proper-list(integer) -- think of octets in [0:256)
;; ==> integer -- sum bytes[i] * 256^i
;; [ with BYTES reversed (hi-order bytes first), we could use the tail-
;; recurring left fold, but most of the program is already there now
;; that I realise the need for quaternary assembly, and I don't want
;; to go through all AB calls and rearrange the arg lists ]
(define (assemble-bytes . bytes)
;; or use kons = (lambda (x y) (bitwise-ior x (arithmetic-shift y 8)))
(fold-right (lambda (x y) (+ x (* 256 y))) 0 bytes))
(define-record-type :image-info
(really-make-image-info format
depth
width/pixel height/pixel
width/dpi height/dpi)
image-info?
(format image-info:format set-format!)
(depth image-info:depth set-depth!)
(width/pixel image-info:width/pixel set-width/pixel!)
(height/pixel image-info:height/pixel set-height/pixel!)
(width/dpi image-info:width/dpi set-width/dpi!)
(height/dpi image-info:height/dpi set-height/dpi!)
)
;; initialize all fields with #f
(define (make-image-info)
(really-make-image-info #f #f #f #f #f #f))
(define-record-discloser :image-info
(lambda (r)
`(image-info ,@(slotlet r 'format image-info:format)
,@(slotlet r 'depth image-info:depth)
,@(slotlet r 'width/pixel image-info:width/pixel)
,@(slotlet r 'height/pixel image-info:height/pixel)
,@(slotlet r 'width/dpi image-info:width/dpi)
,@(slotlet r 'height/dpi image-info:height/dpi)
)))
(define (slotlet r tag get)
(if (get r) `((,tag ,(get r))) '()))
;; img : input-port | byte-vector | byte-stream
;; ==> [width height]
;; width, height : integer -- image size in pixels
(define (image-dimension img)
(let* ((bs (cond ((input-port? img)
(inport->byte-stream img))
((integer? img) ; fdes?
(inport->byte-stream img))
((byte-vector? img)
(byte-vector->byte-stream img))
;; should be a promise
(else img)))
(info (get-image-info bs)))
(if info
(values (image-info:width/pixel info)
(image-info:height/pixel info))
(error "image-dimension : could not extract W x H"))))
;; img : byte-stream
;; ==> info or #f
(define (get-image-info img)
(let ((info (make-image-info)))
(or (fill-info!/gif info img)
(fill-info!/jpeg info img)
(fill-info!/png info img))))
(define (fill-info!/gif info bs)
(receive (bytes foo) (segment-byte-stream bs 0 11)
(and ;; nothing but gif?
(= 11 (byte-vector-length bytes))
(= #x47 (byte-vector-ref bytes 0))
(= #x49 (byte-vector-ref bytes 1))
;; magic 8?a
(= #x46 (byte-vector-ref bytes 2))
(= #x38 (byte-vector-ref bytes 3))
(cond ((= #x37 (byte-vector-ref bytes 4)) ; 87a
(set-format! info 'GIF87A) #t)
((= #x39 (byte-vector-ref bytes 4)) ; 89a
(set-format! info 'GIF89A) #t)
(else #f))
(= #x61 (byte-vector-ref bytes 5))
(begin
(set-width/pixel! info
(assemble-bytes
(byte-vector-ref bytes 6)
(byte-vector-ref bytes 7)))
(set-height/pixel! info
(assemble-bytes
(byte-vector-ref bytes 8)
(byte-vector-ref bytes 9)))
;; colour depth selon global header -- local palettes (of multi-
;; image gifs) may have their own opinion
(set-depth! info
(+ 1 (bitwise-and #x07
(arithmetic-shift
(byte-vector-ref bytes 10) -4))))
info))))
(define (fill-info!/jpeg info bs)
(receive (bytes bs) (segment-byte-stream bs 0 2)
(and
;; nothing but jpeg?
(= 2 (byte-vector-length bytes))
(= #xff (byte-vector-ref bytes 0))
(= #xd8 (byte-vector-ref bytes 1))
(receive/name loop (bytes bs) (segment-byte-stream bs 0 4)
(if (< 4 (byte-vector-length bytes)) #f
(let ((marker (assemble-bytes (byte-vector-ref bytes 1)
(byte-vector-ref bytes 0)))
(size (assemble-bytes (byte-vector-ref bytes 3)
(byte-vector-ref bytes 2))))
(cond ((not (= (bitwise-and marker #xff00) #xff00)) #f)
;; APPx
((and (= marker #xffe0)
(< size 14)) #f)
((= marker #xffe0)
(receive (bytes bs) (segment-byte-stream bs 0 12)
(if (< (byte-vector-length bytes) 12) #f
(begin
(maybe-get-dpi!/jpeg info bytes)
(loop (segment-byte-stream
bs (- size 14) (- size 10)))))))
((and (<= #xffc0 marker #xffcf)
(not (= marker #xffc4))
(not (= marker #xffc8)))
(receive (bytes bs) (segment-byte-stream bs 0 6)
(if (< 6 (byte-vector-length bytes)) #f
(get-most!/jpeg info bytes))))
(else
(loop (segment-byte-stream bs (- size 2) (+ size 2))))
))))
)))
(define (get-most!/jpeg info bytes)
(set-format! info 'JPEG)
(set-depth! info
(* (byte-vector-ref bytes 0)
(byte-vector-ref bytes 5)))
(set-width/pixel! info
(assemble-bytes (byte-vector-ref bytes 4)
(byte-vector-ref bytes 3)))
(set-height/pixel! info
(assemble-bytes (byte-vector-ref bytes 2)
(byte-vector-ref bytes 1)))
info)
;; image-info byte-vector -> any
(define (maybe-get-dpi!/jpeg info bv)
(define (cm->inch x)
(floor (/ (* x 254) 100)))
(and ;; app0 id
(= #x4a (byte-vector-ref bv 0))
(= #x46 (byte-vector-ref bv 1))
(= #x49 (byte-vector-ref bv 2))
(= #x46 (byte-vector-ref bv 3))
(= #x00 (byte-vector-ref bv 4))
;; possibly read physical w x h
(cond ((= 1 (byte-vector-ref bv 7))
(set-width/dpi! info
(assemble-bytes (byte-vector-ref bv 9)
(byte-vector-ref bv 8)))
(set-height/dpi! info
(assemble-bytes (byte-vector-ref bv 11)
(byte-vector-ref bv 10))))
((= 2 (byte-vector-ref bv 7))
(set-width/dpi! info
(cm->inch (assemble-bytes
(byte-vector-ref bv 9)
(byte-vector-ref bv 8))))
(set-height/dpi! info
(cm->inch (assemble-bytes
(byte-vector-ref bv 11)
(byte-vector-ref bv 10))))))))
(define (fill-info!/png info bs)
(receive (bytes foo) (segment-byte-stream bs 0 26)
(and ;; nothing but png?
(= 26 (byte-vector-length bytes))
(= #x89 (byte-vector-ref bytes 0))
(= #x50 (byte-vector-ref bytes 1))
;; png magic
(= #x4e (byte-vector-ref bytes 2))
(= #x47 (byte-vector-ref bytes 3))
(= #x0d (byte-vector-ref bytes 4))
(= #x0a (byte-vector-ref bytes 5))
(= #x1a (byte-vector-ref bytes 6))
(= #x0a (byte-vector-ref bytes 7))
;; get data
(begin
(set-format! info 'PNG)
(set-width/pixel! info
(assemble-bytes (byte-vector-ref bytes 19)
(byte-vector-ref bytes 18)
(byte-vector-ref bytes 17)
(byte-vector-ref bytes 16)))
(set-height/pixel! info
(assemble-bytes (byte-vector-ref bytes 23)
(byte-vector-ref bytes 22)
(byte-vector-ref bytes 21)
(byte-vector-ref bytes 20)))
(set-depth! info
(case (byte-vector-ref bytes 25)
((2 6) (* 3 (byte-vector-ref bytes 24)))
(else (byte-vector-ref bytes 24))))
info))))