@spec calculate_widths(original_width :: pos_integer(), opts :: keyword()) :: [
  pos_integer()
]

Calculate optimal widths dynamically based on original dimensions.

This generates widths at roughly 50% intervals down to a minimum size, which provides good coverage without generating too many files.

Options

• :min_width - Minimum width to generate (default: 320)
• :step_factor - Factor to divide by for each step (default: 1.5)
• :max_variants - Maximum number of variants (default: 6)

Examples

iex> WidthCalculator.calculate_widths(1920)
[320, 480, 720, 1080, 1620, 1920]

iex> WidthCalculator.calculate_widths(800, min_width: 200)
[200, 300, 450, 675, 800]

@spec device_breakpoints() :: [pos_integer()]

Get widths optimized for common device breakpoints.

These match common CSS media query breakpoints:

• 320px - Small phones
• 640px - Large phones / small tablets
• 768px - Tablets
• 1024px - Small desktops / landscape tablets
• 1280px - Desktops
• 1536px - Large desktops
• 1920px - Full HD displays

@spec filter_breakpoints(
  breakpoints :: [pos_integer()],
  original_width :: pos_integer()
) :: [
  pos_integer()
]

Filter breakpoints to only those smaller than the original.

@spec widths_for(original_width :: pos_integer()) :: [pos_integer()]

Get the widths to generate for a given original width.

Returns widths smaller than the original, plus the original width itself.