Question

I tried to find out, but I couldn’t.

A image, for example, 241x76 has a total of 18,316 pixels (241 * 76).
The resize rule is, the amount of pixels cannot pass 10,000.
Then, how can I get the new size keeping the aspect ratio and getting less than 10,000 pixels?

Answer 1

Pseudocode:

pixels = width * height
if (pixels > 10000) then
  ratio = width / height
  scale = sqrt(pixels / 10000)
  height2 = floor(height / scale)
  width2 = floor(ratio * height / scale)
  ASSERT width2 * height2 <= 10000
end if

Remember to use floating-point math for all calculations involving ratio and scale when implementing.

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Python

import math

def capDimensions(width, height, maxPixels=10000):
  pixels = width * height
  if (pixels <= maxPixels):
    return (width, height)

  ratio = float(width) / height
  scale = math.sqrt(float(pixels) / maxPixels)
  height2 = int(float(height) / scale)
  width2 = int(ratio * height / scale)
  return (width2, height2)