Class: Color::CMYK
- Inherits:
-
Object
- Object
- Color::CMYK
- Defined in:
- lib/color/cmyk.rb,
lib/color.rb
Overview
An CMYK colour object. CMYK (cyan, magenta, yellow, and black) colours are based on additive percentages of ink. A CMYK colour of (0.3, 0, 0.8, 0.3) would be mixed from 30% cyan, 0% magenta, 80% yellow, and 30% black. Primarily used in four-colour printing processes.
Constant Summary collapse
- PDF_FORMAT_STR =
The format of a DeviceCMYK colour for PDF. In color-tools 2.0 this will be removed from this package and added back as a modification by the PDF::Writer package.
"%.3f %.3f %.3f %.3f %s"
Class Method Summary collapse
-
.from_fraction(c = 0, m = 0, y = 0, k = 0) ⇒ Object
Creates a CMYK colour object from fractional values 0..1.
-
.from_percent(c = 0, m = 0, y = 0, k = 0) ⇒ Object
Creates a CMYK colour object from percentages.
Instance Method Summary collapse
-
#==(other) ⇒ Object
Compares the other colour to this one.
-
#black ⇒ Object
Returns the black (K) component of the CMYK colour as a percentage value.
-
#black=(kk) ⇒ Object
Sets the black (K) component of the CMYK colour as a percentage value.
-
#c ⇒ Object
Returns the cyan © component of the CMYK colour as a value in the range 0.0 ..
-
#c=(cc) ⇒ Object
Sets the cyan © component of the CMYK colour as a value in the range 0.0 ..
-
#css_hsl ⇒ Object
Present the colour as an HSL HTML/CSS colour string (e.g., “hsl(180, 25%, 35%)”).
-
#css_hsla ⇒ Object
Present the colour as an HSLA (with alpha) HTML/CSS colour string (e.g., “hsla(180, 25%, 35%, 1)”).
-
#css_rgb ⇒ Object
Present the colour as an RGB HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%)”).
-
#css_rgba ⇒ Object
Present the colour as an RGBA (with alpha) HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%, 1)”).
-
#cyan ⇒ Object
Returns the cyan © component of the CMYK colour as a percentage value.
-
#cyan=(cc) ⇒ Object
Sets the cyan © component of the CMYK colour as a percentage value.
-
#html ⇒ Object
Present the colour as an RGB HTML/CSS colour string (e.g., “#aabbcc”).
-
#initialize(c = 0, m = 0, y = 0, k = 0) ⇒ CMYK
constructor
Creates a CMYK colour object from percentages.
- #inspect ⇒ Object
-
#k ⇒ Object
Returns the black (K) component of the CMYK colour as a value in the range 0.0 ..
-
#k=(kk) ⇒ Object
Sets the black (K) component of the CMYK colour as a value in the range 0.0 ..
-
#m ⇒ Object
Returns the magenta (M) component of the CMYK colour as a value in the range 0.0 ..
-
#m=(mm) ⇒ Object
Sets the magenta (M) component of the CMYK colour as a value in the range 0.0 ..
-
#magenta ⇒ Object
Returns the magenta (M) component of the CMYK colour as a percentage value.
-
#magenta=(mm) ⇒ Object
Sets the magenta (M) component of the CMYK colour as a percentage value.
-
#pdf_fill ⇒ Object
Present the colour as a DeviceCMYK fill colour string for PDF.
-
#pdf_stroke ⇒ Object
Present the colour as a DeviceCMYK stroke colour string for PDF.
- #to_cmyk ⇒ Object
-
#to_grayscale ⇒ Object
(also: #to_greyscale)
Converts the CMYK colour to a single greyscale value.
-
#to_hsl ⇒ Object
Converts to RGB then HSL.
-
#to_rgb(use_adobe_method = false) ⇒ Object
Converts the CMYK colour to RGB.
-
#to_yiq ⇒ Object
Converts to RGB then YIQ.
-
#y ⇒ Object
Returns the yellow (Y) component of the CMYK colour as a value in the range 0.0 ..
-
#y=(kk) ⇒ Object
Sets the yellow (Y) component of the CMYK colour as a value in the range 0.0 ..
-
#yellow ⇒ Object
Returns the yellow (Y) component of the CMYK colour as a percentage value.
-
#yellow=(yy) ⇒ Object
Sets the yellow (Y) component of the CMYK colour as a percentage value.
Constructor Details
#initialize(c = 0, m = 0, y = 0, k = 0) ⇒ CMYK
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# File 'lib/color/cmyk.rb', line 63 def initialize(c = 0, m = 0, y = 0, k = 0) @c = c / 100.0 @m = m / 100.0 @y = y / 100.0 @k = k / 100.0 end |
Class Method Details
.from_fraction(c = 0, m = 0, y = 0, k = 0) ⇒ Object
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# File 'lib/color/cmyk.rb', line 42 def self.from_fraction(c = 0, m = 0, y = 0, k = 0) colour = Color::CMYK.new colour.c = c colour.m = m colour.y = y colour.k = k colour end |
Instance Method Details
#==(other) ⇒ Object
Compares the other colour to this one. The other colour will be converted to CMYK before comparison, so the comparison between a CMYK colour and a non-CMYK colour will be approximate and based on the other colour’s #to_cmyk conversion. If there is no #to_cmyk conversion, this will raise an exception. This will report that two CMYK colours are equivalent if all component values are within COLOR_TOLERANCE of each other.
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# File 'lib/color/cmyk.rb', line 30 def ==(other) other = other.to_cmyk other.kind_of?(Color::CMYK) and ((@c - other.c).abs <= Color::COLOR_TOLERANCE) and ((@m - other.m).abs <= Color::COLOR_TOLERANCE) and ((@y - other.y).abs <= Color::COLOR_TOLERANCE) and ((@k - other.k).abs <= Color::COLOR_TOLERANCE) end |
#black ⇒ Object
Returns the black (K) component of the CMYK colour as a percentage value.
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# File 'lib/color/cmyk.rb', line 262 def black @k * 100.0 end |
#black=(kk) ⇒ Object
Sets the black (K) component of the CMYK colour as a percentage value.
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# File 'lib/color/cmyk.rb', line 271 def black=(kk) @k = Color.normalize(kk / 100.0) end |
#c ⇒ Object
Returns the cyan © component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 207 def c @c end |
#c=(cc) ⇒ Object
Sets the cyan © component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 216 def c=(cc) @c = Color.normalize(cc) end |
#css_hsl ⇒ Object
Present the colour as an HSL HTML/CSS colour string (e.g., “hsl(180, 25%, 35%)”). Note that this will perform a #to_hsl operation using the default conversion formula.
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# File 'lib/color/cmyk.rb', line 106 def css_hsl to_hsl.css_hsl end |
#css_hsla ⇒ Object
Present the colour as an HSLA (with alpha) HTML/CSS colour string (e.g., “hsla(180, 25%, 35%, 1)”). Note that this will perform a #to_hsl operation using the default conversion formula.
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# File 'lib/color/cmyk.rb', line 113 def css_hsla to_hsl.css_hsla end |
#css_rgb ⇒ Object
Present the colour as an RGB HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%)”). Note that this will perform a #to_rgb operation using the default conversion formula.
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# File 'lib/color/cmyk.rb', line 92 def css_rgb to_rgb.css_rgb end |
#css_rgba ⇒ Object
Present the colour as an RGBA (with alpha) HTML/CSS colour string (e.g., “rgb(0%, 50%, 100%, 1)”). Note that this will perform a #to_rgb operation using the default conversion formula.
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# File 'lib/color/cmyk.rb', line 99 def css_rgba to_rgb.css_rgba end |
#cyan ⇒ Object
Returns the cyan © component of the CMYK colour as a percentage value.
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# File 'lib/color/cmyk.rb', line 202 def cyan @c * 100.0 end |
#cyan=(cc) ⇒ Object
Sets the cyan © component of the CMYK colour as a percentage value.
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# File 'lib/color/cmyk.rb', line 211 def cyan=(cc) @c = Color.normalize(cc / 100.0) end |
#html ⇒ Object
Present the colour as an RGB HTML/CSS colour string (e.g., “#aabbcc”). Note that this will perform a #to_rgb operation using the default conversion formula.
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# File 'lib/color/cmyk.rb', line 85 def html to_rgb.html end |
#inspect ⇒ Object
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# File 'lib/color/cmyk.rb', line 187 def inspect "CMYK [%.2f%%, %.2f%%, %.2f%%, %.2f%%]" % [ cyan, magenta, yellow, black ] end |
#k ⇒ Object
Returns the black (K) component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 267 def k @k end |
#k=(kk) ⇒ Object
Sets the black (K) component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 276 def k=(kk) @k = Color.normalize(kk) end |
#m ⇒ Object
Returns the magenta (M) component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 227 def m @m end |
#m=(mm) ⇒ Object
Sets the magenta (M) component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 236 def m=(mm) @m = Color.normalize(mm) end |
#magenta ⇒ Object
Returns the magenta (M) component of the CMYK colour as a percentage value.
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# File 'lib/color/cmyk.rb', line 222 def magenta @m * 100.0 end |
#magenta=(mm) ⇒ Object
Sets the magenta (M) component of the CMYK colour as a percentage value.
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# File 'lib/color/cmyk.rb', line 231 def magenta=(mm) @m = Color.normalize(mm / 100.0) end |
#pdf_fill ⇒ Object
Present the colour as a DeviceCMYK fill colour string for PDF. This will be removed from the default package in color-tools 2.0.
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# File 'lib/color/cmyk.rb', line 72 def pdf_fill PDF_FORMAT_STR % [ @c, @m, @y, @k, "k" ] end |
#pdf_stroke ⇒ Object
Present the colour as a DeviceCMYK stroke colour string for PDF. This will be removed from the default package in color-tools 2.0.
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# File 'lib/color/cmyk.rb', line 78 def pdf_stroke PDF_FORMAT_STR % [ @c, @m, @y, @k, "K" ] end |
#to_cmyk ⇒ Object
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# File 'lib/color/cmyk.rb', line 183 def to_cmyk self end |
#to_grayscale ⇒ Object Also known as: to_greyscale
Converts the CMYK colour to a single greyscale value. There are undoubtedly multiple methods for this conversion, but only a minor variant of the Adobe conversion method will be used:
g = 1.0 - min(1.0, 0.299 * c + 0.587 * m + 0.114 * y + k)
This treats the CMY values similarly to YIQ (NTSC) values and then adds the level of black. This is a variant of the Adobe version because it uses the more precise YIQ (NTSC) conversion values for Y (intensity) rather than the approximates provided by Adobe (0.3, 0.59, and 0.11).
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# File 'lib/color/cmyk.rb', line 174 def to_grayscale c = 0.299 * @c.to_f m = 0.587 * @m.to_f y = 0.114 * @y.to_f g = 1.0 - [1.0, c + m + y + @k].min Color::GrayScale.from_fraction(g) end |
#to_hsl ⇒ Object
Converts to RGB then HSL.
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# File 'lib/color/cmyk.rb', line 197 def to_hsl to_rgb.to_hsl end |
#to_rgb(use_adobe_method = false) ⇒ Object
Converts the CMYK colour to RGB. Most colour experts strongly suggest that this is not a good idea (some even suggesting that it’s a very bad idea). CMYK represents additive percentages of inks on white paper, whereas RGB represents mixed colour intensities on a black screen.
However, the colour conversion can be done, and there are two different methods for the conversion that provide slightly different results. Adobe PDF conversions are done with the first form.
# Adobe PDF Display Formula
r = 1.0 - min(1.0, c + k)
g = 1.0 - min(1.0, m + k)
b = 1.0 - min(1.0, y + k)
# Other
r = 1.0 - (c * (1.0 - k) + k)
g = 1.0 - (m * (1.0 - k) + k)
b = 1.0 - (y * (1.0 - k) + k)
If we have a CMYK colour of [33% 66% 83% 25%], the first method will give an approximate RGB colour of (107, 23, 0) or #6b1700. The second method will give an approximate RGB colour of (128, 65, 33) or #804121. Which is correct? Although the colours may seem to be drastically different in the RGB colour space, they are very similar colours, differing mostly in intensity. The first is a darker, slightly redder brown; the second is a lighter brown.
Because of this subtlety, both methods are now offered for conversion. The Adobe method is not used by default; to enable it, pass true
to #to_rgb.
Future versions of Color may offer other conversion mechanisms that offer greater colour fidelity, including recognition of ICC colour profiles.
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# File 'lib/color/cmyk.rb', line 151 def to_rgb(use_adobe_method = false) if use_adobe_method r = 1.0 - [1.0, @c + @k].min g = 1.0 - [1.0, @m + @k].min b = 1.0 - [1.0, @y + @k].min else r = 1.0 - (@c.to_f * (1.0 - @k.to_f) + @k.to_f) g = 1.0 - (@m.to_f * (1.0 - @k.to_f) + @k.to_f) b = 1.0 - (@y.to_f * (1.0 - @k.to_f) + @k.to_f) end Color::RGB.from_fraction(r, g, b) end |
#to_yiq ⇒ Object
Converts to RGB then YIQ.
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# File 'lib/color/cmyk.rb', line 192 def to_yiq to_rgb.to_yiq end |
#y ⇒ Object
Returns the yellow (Y) component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 247 def y @y end |
#y=(kk) ⇒ Object
Sets the yellow (Y) component of the CMYK colour as a value in the range 0.0 .. 1.0.
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# File 'lib/color/cmyk.rb', line 256 def y=(kk) @y = Color.normalize(kk) end |
#yellow ⇒ Object
Returns the yellow (Y) component of the CMYK colour as a percentage value.
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# File 'lib/color/cmyk.rb', line 242 def yellow @y * 100.0 end |