ImageMagick: The Fx Special Effects Image Operator

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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), @@ -231,7 +249,7 @@

math functions:

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()

+ sign(), sin(), sinc(), sinh(), sqrt(), tan(), tanh(), trunc()

channel functions:

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

color names:

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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:

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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

$magick> convert xc:'rgb(25%,50%,75%)' rose: -colorspace rgb \
-format 'Red channel of NW corner of image # %[fx:t] is %[fx: s]' info:Red channel of NW corner of image # 0 is 0.250004
Red channel of NW corner of image # 1 is 0.188235

Use %[fxc: ] if your expression is a constant (e.g. %[fxc:page.x/2]. The result is cached and the cached result returned rather than evaluating the expression each time.

The color-escape %[pixel: ] is evaluated once per image and per color channel in that image (-channel is ignored), The values generated are then converted into a color string (a named color or hex color value). The symbols i and j are set to zero, and s and t refer to each successively current image and index.