Question

在GIMP UI中，有一个应用阈值功能（GIMP 2.6），它有一个名为Auto的选项。这会自动为图像计算适当的下限阈值。此功能/选项是否可用于插件？ gimp-threshold和gimp-histogram函数似乎没有这个选项。

Answer 1

这是我最终使用的解决方案。仅适用于灰度图像。其算法与gimphistogram.c中的gimp_histogram_get_threshold函数相同。

http://git.gnome.org/browse/gimp/tree/app/base/gimphistogram.c

(define (auto-threshold imagePath)
    (let*
        (
            (theImage (car (gimp-file-load
                                    RUN-NONINTERACTIVE
                                    imagePath
                                    imagePath
                            )
                    )
            )

            (theDrawable (car  (gimp-image-get-active-drawable theImage)))
            (hist (get-hist theDrawable 0))
        )
        (get-auto-threshold hist)
    )
)

;returns the threshold 
(define (get-auto-threshold hist)
    (let*
        (
            (hist_max (vector-ref hist 0))
            (chist (make-vector 256))
            (cmom (make-vector 256))
            (maxval 255) ;end - start
            (i 1)
            (tmp )
            (chist_max)
            (cmom_max)
            (bvar_max 0)
            (threshold 127)
        )

        (vector-set! chist 0 (vector-ref hist 0))
        (vector-set! cmom 0 0)

        (set! i 1)
        (while (<= i maxval)
            (if (> (vector-ref hist i) hist_max)
                (set! hist_max (vector-ref hist i))
            )
            (vector-set! chist i (+ (vector-ref chist (- i 1)) (vector-ref hist i)) )
            (vector-set! cmom i (+ (vector-ref cmom (- i 1)) (* i (vector-ref hist i))) )
            (set! i (+ i 1))
        )

        (set! chist_max (vector-ref chist maxval))
        (set! cmom_max (vector-ref cmom maxval))

        (set! i 0)      
        (while (< i maxval)
        (if (and (> (vector-ref chist i) 0) (< (vector-ref chist i) chist_max) ) 
            (let* 
               ((bvar (/ (vector-ref cmom i) (vector-ref chist i))))

               (set! bvar (- bvar (/ (- cmom_max (vector-ref cmom i)) (- chist_max (vector-ref chist i)) ) ))
               (set! bvar (* bvar bvar))
               (set! bvar (* bvar (vector-ref chist i)) )
               (set! bvar (* bvar (- chist_max (vector-ref chist i)) ))

               (if (> bvar bvar_max) 
                  (begin
                    (set! threshold i)
                    (set! bvar_max bvar)
                  )
                )

            )   
        )
        (set! i (+ i 1))
    )

    threshold
)   


)

;returns the raw histogram  with values 0-1 as an array
(define (get-hist drawable chan)
(let* (
(i 0)
(hist (make-vector 256))
)
(set! i 0)
(while (< i 256)
(vector-set! hist i (car (cddddr (gimp-histogram drawable chan i i))))
(set! i (+ i 1))
)
hist
)
)

Answer 2

不幸的是，从GIMP 2.6版开始，此功能不会暴露给过程数据库（API），因此无法在脚本fu或Python脚本中使用。

gimp script-fu中的自动阈值功能

2 个答案: