使用PIL为jpg图像着色

Question

I have written a python code using PIL and Tkinter where I display an image and put a red circle on the image where a user clicked. Here is the relevant code.

def paint_img(event, canvas):
    x, y = event.x, event.y
    image_draw.ellipse((x-10, y-10, x+10, y+10), fill='red')
    canvas._image_tk = ImageTk.PhotoImage(pilImg)
    canvas.itemconfigure(canvas._image_id, image=canvas._image_tk)

It seems that it works with some images, but in some cases it displays a grey circle. I used identify on the test images, for the successful one the output is

totestcolor.jpg JPEG 561x549 561x549+0+0 8-bit DirectClass 18.3kb 

for the unsuccessful one, the output is:

totestcolor1.jpg JPEG 1533x1095 1533x1095+0+0 8-bit PseudoClass 256c 70.4kb  

I want to know why this is happening and if there is any way to output a red circle for the unsuccessful image as well.

Answer 1

That's because the original image is grayscale. You can convert it to full RGB before drawing the red circle. In the PIL library, it is code like this:

pilImg = pilImg.convert("RGB")   # or "RGBA" to keep transparency