Multiple images into a Texture2D with transparency

I'm combining multiple images into one Texture2d, but any top-layer transparency pixels simply overwrite previously loaded images (instead of combining). Is there an easier way to combine them than my hack way shown below? Thanks.

                 t.SetPixels(scene_select_button_style.normal.background.GetPixels());
                 t.Apply();
                
                 Color[] c = daisy_texture.GetPixels(daisies*128,0,128,32);
                 for (int k = 0; k < 32; k++)
                     for (int l = 0; l < 128; l++)
                         if (c[k * 128+l].a > 0)
                             t.SetPixel(0 + l, 30 + k, c[k * 128+l]);
                 t.Apply();