if you want to do some changes in a image channel, you should convert it to a raw-32bit and then start to messing with RGBA blocks (or 64bit, 16-bit? 8-bit? i hope 64-bit color dream never came true for black future!)
if you want to deal with a picture, you have to use a photo editor, paint.NET is a free one
you can convert your image with texconv.exe
"texconv.qgp" -y -ft TGA -m 1 "my_image.png" -o "output_folder"
normal transparency (full, i mean no alpha) is 0xFF (255)
and alpha colors are between 00 (full alpha) and 0xFF (full color)
use below script on 32-bit tga files to make transparency colors to full colors
get FILE_NAMER filename
string FILE_NAME = ""
string FILE_NAME + "transparency_fixer"
string FILE_NAME + \
string FILE_NAME + FILE_NAMER
get SIZER asize
xmath PIXEL_COUNT "(SIZER - 18) / 4"
log MEMORY_FILE1 0 SIZER
goto 18 MEMORY_FILE1
for i = 0 < PIXEL_COUNT
get RGB_COLOR threebyte MEMORY_FILE1
get ALPHA_CODE byte MEMORY_FILE1
if ALPHA_CODE > 0x00 & ALPHA_CODE < 0xFF
savepos CURRENT_LOCATION MEMORY_FILE1
math CURRENT_LOCATION - 1
goto CURRENT_LOCATION MEMORY_FILE1
put 0xFF byte MEMORY_FILE1
log FILE_NAME 0 SIZER MEMORY_FILE1