IMAGE_SetBitmap doesn't work with alpha image

Hi, I converted an image which have alpha channel by BmpCvtST.exe. When I try to display image with IMAGE_SetBitmap, fully transparent section of image seems black, half transparent section of image seems ~yellow and non-transparent areas seams fully transparent. How can I fix the issue. By the way If I use IMAGE_SetBitmap function with an image which havent alpha channel it seams as expected.

Thanks in advance.

I try to use 16 bit image with alpha and it is working. But I couldnt figure out why 32bit image did not display right. Does anyone have an idea about the issue?