Some helpful image manipulations

Extract the alpha channel into a new image.

for i in *norm*.tga; do convert -alpha extract $i ${i%.*}_s.png ; done

Discard the alpha channel

for i in *diff*.tga; do convert -alpha off $i ${i%.*}.png ; done

Just convert the format:

convert myfile.{png,jpg}

When encoding values in the alpha channel that are unrelated to rgb, you might often find that tools try to be smart and discard color information where a=0. This is what you can do:

convert image  -channel RGBA -separate  -resize 100x100  -combine  result  

if Target is PNG, you might need to force 32 bit output (i.e. 4 channels):

convert x.tga png32:x.png

Resize a single image to multiple resolutions:

for i in 1024 512 256 128 64 12 16 ; do convert -resize $ix$i input.jpg out$i.jpg;done