Class: PSD::ChannelImage

Inherits:
Image
  • Object
show all
Includes:
ImageFormat::LayerRAW, ImageFormat::LayerRLE
Defined in:
lib/psd/channel_image.rb

Overview

Represents an image for a single layer, which differs slightly in format from the full size preview image.

Constant Summary

Constants inherited from Image

Image::COMPRESSIONS

Instance Attribute Summary collapse

Attributes inherited from Image

#has_mask, #opacity, #pixel_data

Instance Method Summary collapse

Methods included from Image::Export::PNG

#save_as_png, #to_png

Constructor Details

#initialize(file, header, layer) ⇒ ChannelImage

Returns a new instance of ChannelImage.



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# File 'lib/psd/channel_image.rb', line 14

def initialize(file, header, layer)
  @layer = layer

  @width = @layer.width
  @height = @layer.height

  super(file, header)

  @channels_info = @layer.channels_info
  @has_mask = @channels_info.any? { |chan| chan[:id] == -2 }
  @opacity = @layer.opacity / 255.0
  @mask_data = []
end

Instance Attribute Details

#height ⇒ Object (readonly)

Returns the value of attribute height.



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# File 'lib/psd/channel_image.rb', line 12

def height
  @height
end

#mask_data ⇒ Object (readonly)

Returns the value of attribute mask_data.



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# File 'lib/psd/channel_image.rb', line 12

def mask_data
  @mask_data
end

#width ⇒ Object (readonly)

Returns the value of attribute width.



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# File 'lib/psd/channel_image.rb', line 12

def width
  @width
end

Instance Method Details

#channels ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 35

def channels
  @layer.channels
end

#parse ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 39

def parse
  PSD.logger.debug "Layer = #{@layer.name}, Size = #{width}x#{height}"
  PSD.logger.debug @channels_info

  @chan_pos = 0
  @channels_info.each do |ch_info|
    @ch_info = ch_info
    if ch_info[:length] <= 0
      parse_compression! and next
    end

    # If the ID of this current channel is -2, then we assume the dimensions
    # of the layer mask.
    if ch_info[:id] < -1
      @width = @layer.mask.width
      @height = @layer.mask.height
    else
      @width = @layer.width
      @height = @layer.height
    end

    @length = @width * @height

    start = @file.tell

    PSD.logger.debug "Channel ##{ch_info[:id]}, length = #{ch_info[:length]}"
    parse_image_data!

    finish = @file.tell

    if finish != start + ch_info[:length]
      PSD.logger.error "Read incorrect number of bytes for channel ##{ch_info[:id]}. Expected = #{ch_info[:length]}, Actual = #{finish - start}"
      @file.seek start + ch_info[:length]
    end
  end

  if @channel_data.length != (@length * @channels_info.length)
    PSD.logger.error "#{@channel_data.length} read; expected #{@length}"
  end

  @width = @layer.width
  @height = @layer.height

  parse_user_mask
  process_image_data
end

#parse_image_data! ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 86

def parse_image_data!
  @compression = parse_compression!

  case @compression
  when 0 then parse_raw!
  when 1 then parse_rle!
  when 2, 3 then parse_zip!
  else
    PSD.logger.error "Unknown image compression: #{@compression}. Attempting to skip."
    @file.seek(@end_pos)
  end
end

#parse_user_mask ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 99

def parse_user_mask
  return unless has_mask?

  mask_id = -2

  PSD.logger.debug "Using mask in channel #{mask_id}"

  channel = @channels_info.select { |c| c[:id] == mask_id }.first
  index = @channels_info.index { |c| c[:id] == mask_id }
  return if channel.nil?

  start = @channel_length * index
  length = @layer.mask.width * @layer.mask.height
  PSD.logger.debug "Copying user mask: #{length} bytes at #{start}"

  @mask_data = @channel_data[start, length]

  if @mask_data.length != length
    PSD.logger.error "Mask length is incorrect. Expected = #{length}, Actual = #{@mask_data.length}"
  end
end

#skip ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 28

def skip
  PSD.logger.debug "Skipping channel image data. Layer = #{@layer.name}"
  @channels_info.each do |ch|
    @file.seek ch[:length], IO::SEEK_CUR
  end
end