Create a title with two colors in RMagick

Question

I need to create a caption for a picture using two colors, all the words are in black except one in other color...

I've been reading the docs of RMagick I can't find a way of doing this... What I'm using right now to create the text is:

txt_name = Draw.new
image.annotate(txt_name, 0,0,0,0, "This RED has to be in red") do
    self.gravity = Magick::NorthGravity
    self.pointsize = 20
    self.fill = '#000000'
    txt_name.font_weight = 100
    self.font_family = 'Arial'
end

Any idea?? Or something to read so I can make this work??

Thanks!

Answer 1

Something like the following should work for you. (Please note that this is just to show you the process; I wouldn't recommend putting code like this into production. This is begging to be put in its own class EDIT: see below):

draw               = Magick::Draw.new

Set all of the text attributes on the draw object:

draw.pointsize     = 20
draw.fill          = '#000000'
draw.gravity       = Magick::NorthGravity
draw.font_weight   = 100
draw.font_family   = "Arial"
draw.font_style    = Magick::NormalStyle

Get your image object (this one is just a new blank image):

image              = Magick::Image.new(300,200)

Set up the strings and measure them with get_type_metrics:

black_text         = "This "
red_text           = "RED"
remainder          = " has to be in red"
black_text_metrics = draw.get_type_metrics(black_text)
red_text_metrics   = draw.get_type_metrics(red_text)
remainder_metrics  = draw.get_type_metrics(remainder)

Annotate with the black text:

draw.annotate(image, 
              black_text_metrics.width, 
              black_text_metrics.height,
              10,10,black_text)

Change the color to red and add the red text:

draw.fill = "#ff0000"
draw.annotate(image,
              red_text_metrics.width,
              red_text_metrics.height,
              10 + black_text_metrics.width, # x value set to the initial offset plus the width of the black text
              10, red_text)

Change the color back to black and add the remainder of the text:

draw.fill = "#000000"
draw.annotate(image,
              remainder_metrics.width,
              remainder_metrics.height,
              10 + black_text_metrics.width + red_text_metrics.width,
              10, remainder)

Edit: This may give you an idea of how you could structure this a bit nicer:

TextFragment = Struct.new(:string, :color)

class Annotator
  attr_reader :text_fragments
  attr_accessor :current_color

  def initialize(color = nil)
    @current_color  = color || "#000000"
    @text_fragments = []
  end

  def add_string(string, color = nil)
    text_fragments << TextFragment.new(string, color || current_color)
  end
end


class Magick::Draw
  def annotate_multiple(image, annotator, x, y)
    annotator.text_fragments.each do |fragment|
      metrics   = get_type_metrics(fragment.string)
      self.fill = fragment.color
      annotate(image, metrics.width, metrics.height, x, y, fragment.string)
      x += metrics.width
    end
  end
end

and a usage example:

image            = Magick::Image.new(300,200)
draw             = Magic::Draw.new
draw.pointsize   = 24
draw.font_family = "Arial"
draw.gravity     = Magick::NorthGravity
annotator        = Annotator.new #using the default color (black)

annotator.add_string "Hello "
annotator.add_string "World", "#ff0000"
annotator.add_string "!"

draw.annotate_multiple(image, annotator, 10, 10)