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PATTERN DESCRIPTION: This pattern provides a quick visual evaluation of display performance based on AAPM Report 270 recommendations. MAIN FEATURES: - 18 grayscale squares (3 rows × 6 columns) covering gray levels 0-255 - Each square contains modulation patterns of vertical bars on a 6-pixel period - Upper-left sub-squares: -5 gray levels contrast (darker bars) - Lower-right sub-squares: +5 gray levels contrast (lighter bars) - Special cases: First square (GL 0) and last square (GL 255) use ±3 contrast LARGE SQUARES (bottom): - Three 256×256 squares: Black (0), Mid-gray (128), White (255) - For luminance measurements and uniformity assessment - Can be used for bad pixel detection GRADIENT BAR (bottom): - Continuous 0-255 gradient spanning full width - Line patterns on right side verify pixel mapping - Useful for detecting bit depth issues and contouring artifacts CONTROLS: - Click and drag: Pan the pattern in any direction - Mouse wheel: Zoom in/out (1x to 10x) - ⟲ button (top-left) or R: Reset zoom and panning to default - ? button or H: Show/hide this help - Window resize: Automatically resets view to fit new window size NOTES: - Bar and line-pair periods are fixed in display pixels and do not change with zoom - Corner gradient patterns maintain fixed 2-pixel period - Pattern scales to fit window height while maintaining aspect ratio - Bar patterns are drawn in display pixels at any OS scaling or browser zoom. A browser that cannot report the exact canvas size at a fractional scaling shows a notice on load. - macOS: use the display's default resolution. Scaled resolutions resample the whole screen after the browser draws, which no web page can detect or undo. USAGE: - On a DICOM-conformant display, all 18 5-level modulation patterns should be about equally visible - The corner patterns (upper-left of first square, lower-right of last square) have lower contrast (3 gray levels) and may only be visible on the highest-performance displays - The high-contrast line pairs in the lower-right corner should appear crisp, and the ramp should be smooth with no jumps or artifacts