How to convert bounding box (x1, y1, x2, y2) to YOLO Style (X, Y, W, H)

Here's code snipet in python to convert x,y coordinates to yolo format

def convert(size, box):
    dw = 1./size[0]
    dh = 1./size[1]
    x = (box[0] + box[1])/2.0
    y = (box[2] + box[3])/2.0
    w = box[1] - box[0]
    h = box[3] - box[2]
    x = x*dw
    w = w*dw
    y = y*dh
    h = h*dh
    return (x,y,w,h)

im=Image.open(img_path)
w= int(im.size[0])
h= int(im.size[1])


print(xmin, xmax, ymin, ymax) #define your x,y coordinates
b = (xmin, xmax, ymin, ymax)
bb = convert((w,h), b)

Check my sample program to convert from LabelMe annotation tool format to Yolo format https://github.com/ivder/LabelMeYoloConverter

for those looking for the reverse of the question (yolo format to normal bbox format)

def yolobbox2bbox(x,y,w,h):
    x1, y1 = x-w/2, y-h/2
    x2, y2 = x+w/2, y+h/2
    return x1, y1, x2, y2