Pixel 和 DPI

DPI : Dots Per Inch， 每一英吋的點數量

• 電腦解析度為 1024 x 768 pixel , 72 dpi
  換算為：
  ( 1024 / 72 ) x ( 768 / 72 ) = 14.2 inch x 10.6 inch1 inch = 2.54 cm
  ( 14.2 x 2.54 ) x ( 10.6 x 2.54 ) = 36 cm x 26 cm
  ref : Here

• 1600 x 1200 pixel = 192萬pixel，以300dpi的影像解析度列印，則可印出 5.3"x4" 的成品
  計算方法：
  1600 像素 / 300 dpi= 5.3" (inch)
  1200 像素 / 300 dpi= 4" (inch)
  ref: Here

• X-DPI =  x pixel  /   x-physical screen size (inch)
  Y-DPI =  y pixel  /   x-physical screen size (inch)

另外，根據 android cdd:
ldpi -    120 pixels/inch; dpi scale =  0.75 (4 dpi = 3 pixels)
mdpi -  160 pixels/inch; dpi scale = 1       (1 dpi = 1 pixel)   <- base="" font="">
tvdpi -  213 pixels/inch; dpi scale 約 0.75 ( 4 dpi =  3 pixel)
hdpi -   240 pixels/inch; dpi scale = 1.5    (2 dpi = 3 pixels)
xhdpi - 320 pixels/inch; dpi scale = 2       (1 dpi = 2 pixels)
4.4新增
400dpi - 400 pixels/inch; dpi scale = 2.5  ( 2 dpi =  5 pixels)
xxhdpi - 480 pixels/inch; dpi scale =  3     ( 1 dpi =  3 pixels)
xxxhdpi - 640 pixels/inch; dpi scale = 4     ( 1 dpi =  4 pixels)

ldpi:mdpi:hdpi:xhdpi:xxhdpi=3:4:6:8:12，相隔數字之間是乘以2倍