Module: Pdfrb::Color::ICCValidator

Defined in:
lib/pdfrb/color/icc_validator.rb

Overview

Validates an ICC profile binary against the structural rules in ICC.1:2022 ยง7. The validator checks:

* Profile size >= 128 (header) + 4 (tag count)
* 'acsp' signature at offset 36
* Profile version is 2.x, 4.x, or 5.x
* Device class is one of the known classes
* Color space is one of the known spaces
* Tag table offsets don't exceed the file size

Returns an Array of Violation strings (empty if valid).

Constant Summary collapse

VALID_VERSIONS = 
[(2.0..2.99), (4.0..4.99), (5.0..5.99)].freeze
VALID_DEVICE_CLASSES = 
%w[
  scnr mntr prtr link spac abst nmcl nkpr
].freeze
VALID_COLOR_SPACES = 
%w[
  XYZ Lab Luv YCbCr Yxy RGB GRAY HSV HLS CMYK CMY 2CLR 3CLR
  4CLR 5CLR 6CLR 7CLR 8CLR 9CLR ACLR BCLR CCLR DCLR ECLR FCLR
].freeze

Class Method Summary collapse

Class Method Details

.valid?(profile_bytes) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pdfrb/color/icc_validator.rb', line 64

def valid?(profile_bytes)
  validate(profile_bytes).empty?
end

.validate(profile_bytes) ⇒ Object 



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# File 'lib/pdfrb/color/icc_validator.rb', line 27

def validate(profile_bytes)
  violations = []
  unless profile_bytes.is_a?(::String) && profile_bytes.bytesize >= 132
    violations << "ICC profile too small (need >= 132 bytes, got #{profile_bytes&.bytesize})"
    return violations
  end

  unless profile_bytes.byteslice(36, 4) == "acsp"
    violations << "ICC profile signature at offset 36 is not 'acsp'"
  end

  version_hi = profile_bytes.getbyte(8)
  version_lo = profile_bytes.getbyte(9)
  version = (version_hi * 1.0) + (version_lo / 16.0 / 10.0)
  unless VALID_VERSIONS.any? { |range| range.cover?(version) }
    violations << "ICC profile version #{version} not in 2.x/4.x/5.x"
  end

  device_class = profile_bytes.byteslice(12, 4).to_s.strip
  unless VALID_DEVICE_CLASSES.include?(device_class)
    violations << "ICC device class '#{device_class}' is not recognised"
  end

  color_space = profile_bytes.byteslice(16, 4).to_s.strip
  unless VALID_COLOR_SPACES.include?(color_space)
    violations << "ICC color space '#{color_space}' is not recognised"
  end

  # Tag table sanity check
  tag_count = profile_bytes.unpack1("N", offset: 128)
  if tag_count > 256
    violations << "ICC tag count #{tag_count} looks bogus (max 256)"
  end

  violations
end