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pdftract/notes/pdftract-44f6.md
jedarden 6ea0b0aa54 feat(pdftract-44f6): implement GraphicsState with 13 fields, Color enum, and matrix ops 
Implements the complete graphics state per PDF spec section 8.4:

- Color enum with 5 variants (DeviceGray/RGB/CMYK, Spot, Other)
- Color::to_css_hex() for JSON serialization (returns None for Spot/Other)
- GraphicsState struct with all 13 fields (ctm, text_matrix, text_line_matrix,
  font, font_size, char_spacing, word_spacing, horiz_scaling, leading,
  text_rise, text_rendering_mode, fill_color, stroke_color)
- GraphicsState::initial() returning default state (identity CTM, black colors)
- Matrix operations: scale(), translate(), rotate(), invert()
- Manual Debug impl for GraphicsState (Font doesn't implement Debug)

All acceptance criteria PASS:
- initial() has identity CTM, font_size 0.0, fill_color DeviceGray(0.0)
- Clone produces deep-equal value
- Color::DeviceRGB([1.0, 0.0, 0.0]).to_css_hex() == Some("#ff0000")
- Color::Spot returns None
- Matrix multiply identity*identity within 1e-10

Closes: pdftract-44f6

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
2026-05-24 15:49:50 -04:00

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pdftract-44f6: GraphicsState struct + Color enum + matrix initialization

Summary

Implemented the complete GraphicsState struct with all 13 fields per PDF spec section 8.4, plus the Color enum with CSS hex serialization and matrix operations.

Changes Made

File: crates/pdftract-core/src/graphics_state.rs

  1. Added Color enum with 5 variants:

    • DeviceGray(f32) - single grayscale component
    • DeviceRGB([f32; 3]) - RGB color
    • DeviceCMYK([f32; 4]) - CMYK color
    • Spot(Arc<str>, f32) - spot color with tint
    • Other - other color spaces

  2. Added Color::to_css_hex() method:

    • Converts DeviceGray/RGB/CMYK to "#rrggbb" format
    • Returns None for Spot/Other
    • Includes clamp for safety
    • CMYK→RGB uses naive formula: R=(1-C)*(1-K)

  3. Extended GraphicsState struct with all 13 fields:

    • ctm: Matrix3x3 - current transformation matrix
    • text_matrix: Matrix3x3 - Tm
    • text_line_matrix: Matrix3x3 - Tlm
    • font: Option<Arc<Font>> - current font
    • font_size: f64 - Tf
    • char_spacing: f64 - Tc
    • word_spacing: f64 - Tw
    • horiz_scaling: f64 - Tz (default 100)
    • leading: f64 - TL
    • text_rise: f64 - Ts
    • text_rendering_mode: u8 - Tr (0-7)
    • fill_color: Color - fill color
    • stroke_color: Color - stroke color

  4. Added GraphicsState::initial() returning default state:

    • Identity CTM, text_matrix, text_line_matrix
    • font: None
    • font_size: 0.0
    • All spacings: 0.0
    • horiz_scaling: 100.0
    • text_rendering_mode: 0
    • fill/stroke_color: DeviceGray(0.0) (black)

  5. Added matrix operations to Matrix3x3:

    • scale(sx, sy) - create scale matrix
    • translate(tx, ty) - create translation matrix
    • rotate(angle) - create rotation matrix (angle in radians)
    • invert() - invert matrix, returns None if singular

  6. Implemented Debug manually for GraphicsState:

    • Font doesn't implement Debug, so we show <Arc<Font>> placeholder

  7. Added comprehensive tests:

    • test_gstate_initial_ctm_is_identity
    • test_gstate_initial_font_size_is_zero
    • test_gstate_initial_fill_color_is_black
    • test_gstate_initial_horiz_scaling_is_100
    • test_gstate_initial_text_matrices_are_identity
    • test_gstate_initial_font_is_none
    • test_gstate_initial_text_rendering_mode_is_0
    • test_gstate_clone_deep_equal
    • test_color_device_rgb_to_css_hex - verifies #ff0000 for red
    • test_color_device_gray_to_css_hex
    • test_color_device_cmyk_to_css_hex
    • test_color_spot_to_css_hex_none
    • test_color_other_to_css_hex_none
    • test_color_device_rgb_clamped
    • test_matrix_scale
    • test_matrix_translate
    • test_matrix_rotate
    • test_matrix_invert_identity
    • test_matrix_invert_translation
    • test_matrix_invert_singular
    • test_identity_multiply_identity
    • test_multiply_within_tolerance

Acceptance Criteria Status

  • ✅ GraphicsState::initial() returns state with ctm == identity
  • ✅ GraphicsState::initial() returns state with font_size == 0.0
  • ✅ GraphicsState::initial() returns state with fill_color == DeviceGray(0.0)
  • ✅ Clone produces a deep-equal value (Arc cloned cheaply)
  • ✅ Color::DeviceRGB([1.0, 0.0, 0.0]).to_css_hex() == Some("#ff0000".into())
  • ✅ Color::Spot("PANTONE".into(), 0.5).to_css_hex() == None
  • ✅ Matrix multiply test: identity * identity == identity within 1e-10

Notes

  • Font doesn't implement Debug, so GraphicsState has a manual Debug impl that shows <Arc<Font>> placeholder for the font field
  • All matrix operations use f64 for precision (INV-30)
  • Color uses f32 for components per PDF spec convention
  • GraphicsState is Clone thanks to Arc (cheap clone for q/Q operators)

References

  • Plan section: Phase 3.1 State struct fields (lines 1444-1460), Color type (lines 1463-1471), CSS hex rules (line 1473)