from PIL import Image

#Attention au chemin vers l'image !!
MonImage = Image.open("P:\\SNT\\IMG\\cinema.jpeg")

Taille = MonImage.size

Image_Sans_Vert = Image.new("RGBA", Taille, (0,0,0,0))

for c in range(Taille[0]):
    for l in range(Taille[1]):
        rgb = MonImage.getpixel((c, l))
        R = rgb[0]
        G = rgb[1]
        B = rgb[2]
        if G < 120 :
            Image_Sans_Vert.putpixel((c, l), (R, G, B, 255))
            
Image_Sans_Vert.show()