'按方向上下键调节对比度
Contrast = 0
DO
FOR y = 0 TO h - 1
FOR x = 0 TO w - 1
a = r(x, y)
a = a + (a - 128) * Contrast / 255
IF a < 0 THEN a = 0
IF a > 255 THEN a = 255
rr = a
a = g(x, y)
a = a + (a - 128) * Contrast / 255
IF a < 0 THEN a = 0
IF a > 255 THEN a = 255
gg = a
a = b(x, y)
a = a + (a - 128) * Contrast / 255
IF a < 0 THEN a = 0
IF a > 255 THEN a = 255
bb = a
PSET (x, 480 - y), _RGB(rr, gg, bb)
NEXT x
NEXT y
aa$ = INKEY$
IF aa$ <> "" THEN
IF LEN(aa$) = 2 THEN
'方向键上键= chr$(0)+"H"
IF MID$(aa$, 2, 1) = "H" THEN Contrast = Contrast + 25 '按a对比度增
IF Contrast > 255 THEN Contrast = 255
'方向键下键= chr$(0)+"P"
IF MID$(aa$, 2, 1) = "P" THEN Contrast = Contrast - 25 '按z对比度减
IF Contrast < -255 THEN Contrast = -255
LOCATE 1, 50
PRINT (aa$), Contrast
END IF
END IF
'(1)、nRGB = RGB + (RGB - Threshold) * Contrast / 255
' 公式中，nRGB表示图像像素新的R、G、B分量，RGB表示图像像素R、G、B分量，Threshold为给定的阈值，
'Contrast为处理过的对比度增量。
LOOP UNTIL aa$ = CHR$(27) '按 esc 退出

顶…

DO
FOR y = 0 TO h - 1
FOR x = 0 TO w - 1
a = r(x, y)
a = a + (a - 128) * Contrast / 255
IF a < 0 THEN a = 0
IF a > 255 THEN a = 255
rr = a
a = g(x, y)
a = a + (a - 128) * Contrast / 255
IF a < 0 THEN a = 0
IF a > 255 THEN a = 255
gg = a
a = b(x, y)
a = a + (a - 128) * Contrast / 255
IF a < 0 THEN a = 0
IF a > 255 THEN a = 255
bb = a
PSET (x, 480 - y), _RGB(rr, gg, bb)
NEXT x
NEXT y
aa$ = INKEY$
IF aa$ <> "" THEN
IF LEN(aa$) = 2 THEN
'方向键上键= chr$(0)+"H"
IF MID$(aa$, 2, 1) = "H" THEN Contrast = Contrast + 25 '按上对比度增
IF Contrast > 255 THEN Contrast = 255
'方向键下键= chr$(0)+"P"
IF MID$(aa$, 2, 1) = "P" THEN Contrast = Contrast - 25 '按下对比度减
IF Contrast < -255 THEN Contrast = -255
END IF
END IF
'(1)、nRGB = RGB + (RGB - Threshold) * Contrast / 255
' 公式中，nRGB表示图像像素新的R、G、B分量，RGB表示图像像素R、G、B分量，Threshold为给定的阈值，
'Contrast为处理过的对比度增量。
LOOP UNTIL aa$ = CHR$(27) '按 esc 退出