how can i save pixel changes in image?

hi

i made pixel value changes in an image , then i save it in a new name, then i wanted to use the new in another code, i checked the pixel values and

rgbValues2 =

   232   240   253

rgbValues1 =

    10   240   253

pixelvalue =

   182   194   208

redvalue =

182

why is that?? shouldn't be the pixelvalue=10 240 253??

Answer 1

[David Young]

Could be because JPEG compression loses information, so a write followed by a read only returns an approximation to the original. Try using a lossless format, such as BMP, instead of JPEG.

Also, do you need to write the image out to a file and read it back anyway? It's usually much more efficient simply to pass the image between functions or scripts in memory, using the name of the variable that refers to it.