why pixels values are unaltered even though after applying double?

when i have applied double to my image the pixel values are not changing they are not coming in the range [0,1]?

Answer 1

[Walter Roberson]

You need im2double for that.

[gayathri rajkumar]

thank u but whats the difference between im2double and double?

[Walter Roberson]

double() applied to an integer converts to the double precision number with the same signed magnitude as the integer. For example A = uint8(17); B = double(A); then afterwards B would be 17.0 -- same numeric value.

im2double() applied to an integer converts to the double precision number with the same relative value for the purposes of images. Images in MATLAB can be represented by uint8, uint16, int16, single, or double. For uint8 and uint16, the values are understood to designate fractions compared to the maximum value of that integer class, so for A = uint8(17); then in an image, A would be interpreted as designating 17/255 of maximum intensity, and im2double() would convert it to 17.0/255.0 = approximately 0.0667 . uint16(17) would represent 17/65535 of maximum intensity and im2double() would convert it to 17.0/65535.0.