can't success in change image extension and size in Matlab

[SerogaM]

I want change file from JPEG to tiff and no use any compression change image size :
the code I wrote is:

f=imread('source_image.jpg');
figure(1)
imshow(f)
imwrite(f,'new_tif_image_file.tif','compression','none','resolution',...
[100 80])
g=imread('new_tif_image_file.tif');
figure(2)
imshow(g)

~~after all these done I look at two images and they look same...
what problem in this code?