class GD2::Palette
Description¶ ↑
Palette objects are associated with an Image and hold the selection of pixel colors available to the Image. This is primarily a concern for Image::IndexedColor images, but their use with Image::TrueColor images is supported for consistency.
Obtaining¶ ↑
Obtain a Palette object from the associated Image:
palette = image.palette
Attributes
Public Instance Methods
Ensure the given color
is present in this palette, allocating
it if necessary. Returns the palette so calls may be stacked.
# File lib/gd2/palette.rb, line 158 def <<(color) exact(color) or allocate(color) self end
Return the color allocated to the specified index
, or
nil if the entry is unallocated.
# File lib/gd2/palette.rb, line 74 def [](index) index = size + index if index < 0 raise RangeError unless (0...size).include? index return nil unless allocated?(index) get_color(index) end
Assign (allocate) the given color
to the palette entry
identified by index
. If the entry was previously allocated to
a different color, every pixel in the image having the given color
index
will effectively be changed to the new color. This
method cannot be used with Image::TrueColor palettes.
# File lib/gd2/palette.rb, line 86 def []=(index, color) raise RangeError unless (0...MAX_COLORS).include? index if color.nil? deallocate(self[index] || Color.new_from_palette(0, 0, 0, 0, index, self)) else ptr = @image.image_ptr ptr[:"red[#{index}]"] = color.red ptr[:"green[#{index}]"] = color.green ptr[:"blue[#{index}]"] = color.blue ptr[:"alpha[#{index}]"] = color.alpha ptr[:"open[#{index}]"] = 0 end end
Assign the given color
to an unoccupied entry in this palette
and return it. Does not check whether the color is already allocated, and
raises an error for Image::IndexedColor palettes if the
palette is full.
# File lib/gd2/palette.rb, line 148 def allocate(color) raise TypeError unless color.kind_of? Color c = SYM[:gdImageColorAllocateAlpha].call(@image.image_ptr, color.red, color.green, color.blue, color.alpha)[0] c == -1 ? raise(Palette::PaletteFullError, 'Palette is full') : get_color(c) end
Return the number of palette entries available to be allocated for new colors.
# File lib/gd2/palette.rb, line 68 def available size - used end
Return the color in this palette that is closest to the given
color
according to Euclidian distance.
# File lib/gd2/palette.rb, line 129 def closest(color) raise TypeError unless color.kind_of? Color c = SYM[:gdImageColorClosestAlpha].call(@image.image_ptr, color.red, color.green, color.blue, color.alpha)[0] c == -1 ? nil : get_color(c) end
Return the color in this palette that is closest to the given
color
according to hue, whiteness, and blackness.
# File lib/gd2/palette.rb, line 138 def closest_hwb(color) raise TypeError unless color.kind_of? Color c = SYM[:gdImageColorClosestHWB].call(@image.image_ptr, color.red, color.green, color.blue)[0] c == -1 ? nil : get_color(c) end
Remove the given color
from this palette.
# File lib/gd2/palette.rb, line 164 def deallocate(color) color = exact(color) unless color.index return nil if color.nil? || color.index.nil? SYM[:gdImageColorDeallocate].call(@image.image_ptr, color.index) nil end
Remove all colors from this palette that are not currently in use by the associated Image. This is an expensive operation. Returns the number of palette entries deallocated.
# File lib/gd2/palette.rb, line 174 def deallocate_unused # implemented by subclass end
Locate the given color
in this palette and return it. Returns
nil if the color is not presently in the palette.
# File lib/gd2/palette.rb, line 113 def exact(color) raise TypeError unless color.kind_of? Color c = SYM[:gdImageColorExactAlpha].call(@image.image_ptr, color.red, color.green, color.blue, color.alpha)[0] c == -1 ? nil : get_color(c) end
Like #exact except an error is raised if the color is not presently in the palette.
# File lib/gd2/palette.rb, line 122 def exact!(color) exact(color) or raise Palette::ColorNotFoundError, "Color #{color} is not in the palette" end
Locate the given color
in this palette and return it if found;
otherwise try to allocate the color
, or if the palette is
full, return a color from the palette that is closest to it.
# File lib/gd2/palette.rb, line 104 def resolve(color) raise TypeError unless color.kind_of? Color c = SYM[:gdImageColorResolveAlpha].call(@image.image_ptr, color.red, color. green, color.blue, color.alpha)[0] c == -1 ? nil : get_color(c) end
Return the maximum number of colors this palette can hold.
# File lib/gd2/palette.rb, line 49 def size MAX_COLORS end
Return the number of colors presently allocated in this palette.
# File lib/gd2/palette.rb, line 60 def used (0...size).inject(0) do |sum, i| sum + (allocated?(i) ? 1 : 0) end end