Problem
Fine diagonal lines produce moiré patterns when reduced to thumbnail size.
Solution
Root Cause / Diagnostic:
High-frequency repetitive diagonal patterns (such as architectural slats, window blinds, or fine clothing weaves) exceed the Nyquist frequency when downsampled. The resulting aliasing manifests as psychedelic, distracting moiré interference patterns across the image.
Actionable Fix:
1. Apply a subtle directional Gaussian blur (radius 0.8–1.5 px) parallel to the offending diagonal lines to attenuate frequencies before downscaling.
2. Downsample master artwork using "Bicubic Sharper (reduction)" or "Bilinear" interpolation, which suppresses geometric moiré interference better than Nearest Neighbor.
3. Check the downsampled image at standard mobile thumbnail sizes (160x90 px) to verify that diagonal patterns resolve smoothly without rainbow moiré ripples.
Pro Tip:
Slightly blur high-frequency diagonal patterns before final downsampling; dropping frequencies below the Nyquist threshold completely eliminates moiré interference.
High-frequency repetitive diagonal patterns (such as architectural slats, window blinds, or fine clothing weaves) exceed the Nyquist frequency when downsampled. The resulting aliasing manifests as psychedelic, distracting moiré interference patterns across the image.
Actionable Fix:
1. Apply a subtle directional Gaussian blur (radius 0.8–1.5 px) parallel to the offending diagonal lines to attenuate frequencies before downscaling.
2. Downsample master artwork using "Bicubic Sharper (reduction)" or "Bilinear" interpolation, which suppresses geometric moiré interference better than Nearest Neighbor.
3. Check the downsampled image at standard mobile thumbnail sizes (160x90 px) to verify that diagonal patterns resolve smoothly without rainbow moiré ripples.
Pro Tip:
Slightly blur high-frequency diagonal patterns before final downsampling; dropping frequencies below the Nyquist threshold completely eliminates moiré interference.