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

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 12

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

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

  super(file, header)

  @channels_info = @layer.channels_info
end

Instance Attribute Details

#height ⇒ Object (readonly)

Returns the value of attribute height.



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# File 'lib/psd/channel_image.rb', line 10

def height
  @height
end

#width ⇒ Object (readonly)

Returns the value of attribute width.



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# File 'lib/psd/channel_image.rb', line 10

def width
  @width
end

Instance Method Details

#channels ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 30

def channels
  @layer.channels
end

#parse ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 34

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

  @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] == -2
      @width = @layer.mask.width
      @height = @layer.mask.height
    else
      @width = @layer.width
      @height = @layer.height
    end

    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
    PSD.logger.error "#{channel_data.length} read; expected #{@length}"
  end

  process_image_data
end

#parse_image_data! ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 75

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. Attempting to skip."
    @file.seek(@end_pos)
  end
end

#skip ⇒ Object 



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# File 'lib/psd/channel_image.rb', line 23

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