ImageMagick: The Fx Special Effects Image Operator

@@ -226,15 +241,15 @@

constants:

e, Epsilon, QuantumRange, QuantumScale, Opaque, Pi, Transparent

Fx operators (in order of precedence):

^ (power), *, /, % (modulo), +, -, +

^ (power), unary -, *, /, % (modulo), +, -, <<, >>, <, <=, >, >=, ==, !=, & (bitwise AND), | (bitwise OR), && (logical AND), || (logical OR), ~ (logical NOT), ?: (ternary conditional)

math functions:

abs(), acos(), alt(), asin(), atan(), atan2(), ceil(), cos(), cosh(), debug(), exp(), floor(), - hypot(), int(), ln(), log(), logtwo(), max(), min(), mod(), pow(), rand(), round(), - sign(), sin(), sinh(), sqrt(), tan(), tanh()

abs(), acos(), airy(), alt(), asin(), atan(), atan2(), ceil(), cos(), cosh(), debug(), exp(), floor(), + hypot(), int(), j0(), j1(), jinc(), ln(), log(), logtwo(), max(), min(), mod(), pow(), rand(), round(), + sign(), sin(), sinc(), sinh(), sqrt(), tan(), tanh(), trunc()

channel functions:

channel(r,g,b,a), channel(c,m,y,k,a)

color names:

@@ -343,6 +358,7 @@

s, t, u, v, n, i, j, w, h, z, r, g, b, a, o, c, y, m, k: symbols

abs(x): absolute value function

acos(x): arc cosine function

airy(x): Airy function (max=1, min=0); airy(x)=[jinc(x)]²=[2*j1(pi*x)/(pi*x)]²

alt(x): sign alternation function (return 1.0 if int(x) is even, -1.0 if int(x) is odd)

asin(x): arc sine function

atan(x): arc tangent function

@@ -357,6 +373,9 @@

floor(x): largest integral value not greater than argument

hypot(x,y): the square root of x²+y²

int(x): greatest integer function (return greatest integer less than or equal to x)

j0(x): Bessel functions of x of the first kind of order 0

j1(x): Bessel functions of x of the first kind of order 1

jinc(x): jinc function (max=1, min=-0.1323); jinc(x)=2*j1(pi*x)/(pi*x)

ln(x): natural logarithm function

log(x): logarithm base 10

logtwo(x): logarithm base 2

@@ -369,10 +388,12 @@

round(): round to integral value, regardless of rounding direction

sign(x): return -1.0 if x is less than 0.0 otherwise 1.0

sin(x): sine function

sinc(x): sinc function (max=1, min=-0.21); sinc(x)=sin(pi*x)/(pi*x)

sinh(x): hyperbolic sine function

sqrt(x): square root function

tan(x): tangent function

tanh(x): hyperbolic tangent function

trunc(x): round to integer, towards zero

The expression semantics include these rules:

@@ -383,8 +404,11 @@

statements are assignments or the final expression to return

an assignment starts a statement, it is not an operator

assignments to built-ins do not throw an exception and have no effect; e.g. r=3.0; r returns the pixel red color value, not 3.0

Unary operators have a lower priority than binary operators, that is, the unary minus (negation) has lower precedence than exponentiation, so -3^2 is interpreted as -(3^2) = -9. Use parentheses to clarify your intent (e.g. (-3)^2 = 9).

Similarly, care must be exercised when using the slash ('/') symbol. The string of characters 1/2x is interpreted as (1/2)x. The contrary interpretation should be written explicitly as 1/(2x). Again, the use of parentheses helps clarify the meaning and should be used whenever there is any chance of misinterpretation.

Source Images

By default, the image to which p, r, g, b, a, etc., are applied is the first image u in the image list, which may also be referenced using s.

It is important to note the special role played by the first image. This is the only image in the image sequence that is modified, any other images being used only for their data. As an illustrative example, comsider the following, and note that the setting -channel red instructs -fx to modify only the red channel; nothing in the green or blue channels will change. It is instructive to ponder why the result is not symmetric.

It is important to note the special role played by the first image. This is the only image in the image sequence that is modified, other images are used only for their data. As an illustrative example, consider the following, and note that the setting -channel red instructs -fx to modify only the red channel; nothing in the green or blue channels will change. It is instructive to ponder why the result is not symmetric.

$magick> convert -channel red logo: -flop logo: -resize "20%" -fx "(u+v)/2" image.jpg