Hey the image is not dark, the actual image is bright but when I embed the image here its darkened, but when I open the image in the different window, its back to normal form , this i am still not able to figure, and well regarding the necessity of scaling, err I tried all the settings and its impossible to reduce the image size to less than 100K with 320x480 resolution, and there are fewer options with the PNG24 format, max was I could reduce it to around 150K :( , regarding the steps i will PM you on how to add the channel but you should know some basics of photoshop for it though
By the way you can add the channel only through Photoshop i think.