Position of images as nodes in networkx plot?-CodePudding

After using

The x,y-positions of the nodes is set as:

pos={
0: [0, 0], 
1: [1, 0], 
2: [2, 0], 
3: [3, 0], 
4: [4, 0], 
5: [5, 0], 
6: [6, 0], 
7: [5, 1]
}

and the code to generate the plot is:

pos:Dict={}
    for nodename in G.nodes:
        pos[nodename]=G.nodes[nodename]["pos"]
    print(f'pos={pos}')
    

    fig=plt.figure(figsize=(1,1))
    ax=plt.subplot(111)
    ax.set_aspect('equal')
    nx.draw_networkx_edges(G,pos,ax=ax)
    

    # plt.xlim(-1,10)
    # plt.ylim(-1.5,1.5)

    trans=ax.transData.transform
    trans2=fig.transFigure.inverted().transform

    piesize=0.3 # this is the image size
    p2=piesize/2.0
    for n in G:
        xx,yy=trans(pos[n]) # figure coordinates
        #print(f'xx,yy={xx,yy}')
        xa,ya=trans2((xx,yy)) # axes coordinates
        print(f'xa,ya={xa,ya}')
        a = plt.axes([xa-p2,ya-p2, piesize, piesize])
        a.set_aspect('equal')
        a.imshow(G.nodes[n]['image'])
        a.axis('off')
    ax.axis('off')
    plt.show()

However, the y-coordinates of the edges does not align with the y-coordinates of the images. I expect this is because the coordinate transformation applied for the plt.axes[[xa-p2... line, is not applied to the edge drawings.

Question

How can I ensure the images are placed on their x,y coordinate positions a figure with size [x_min,x_max,y_min,y_max] whilst ensuring the edges of the networkx Graph also point to the accompaning coordinates?

CodePudding user response：

Try not to set the axes ratio to equal (i.e. remove this line ax.set_aspect('equal')).

Though this will hopefully solve the question, there will probably the additional problem, that the arrow heads are hidden behind the images. A solution is to set the node_size parameter when calling nx.draw_networkx_edges().

When doing so an additional challenge is, that the image size seems to have different length and height values. A workaround is to first draw the vertical edges with a larger node_size. Then add the horizontal edges and set a smaller node_size (the vertical edges will be drawn again, but their arrow heads are hidden behind the image). You will probably have to play around with the values a bit.


pos={
0: [0, 0], 
1: [1, 0], 
2: [2, 0], 
3: [3, 0], 
4: [4, 0], 
5: [5, 0], 
6: [6, 0], 
7: [5, 1]
}

img=mpimg.imread(sample_img_path)
G=nx.DiGraph()
G.add_node(0,image=img)
G.add_node(1,image=img)
G.add_node(2,image=img)
G.add_node(3,image=img)
G.add_node(4,image=img)
G.add_node(5,image=img)
G.add_node(6,image=img)
G.add_node(7,image=img)


fig=plt.figure(figsize=(12,3))
ax=plt.subplot(111)
#ax.set_aspect('equal') # <-- not set the aspect ratio to equal

# draw vertical edges using a larger node size
G.add_edge(4,7)
G.add_edge(5,7)
G.add_edge(6,7)
nx.draw_networkx_edges(G,pos,ax=ax, node_size=8000, arrowsize=30)

# add the horizontal edges with a smaller node size
G.add_edge(0,1)
G.add_edge(1,2)
G.add_edge(2,3)
G.add_edge(3,4)
G.add_edge(4,5)
G.add_edge(6,5)
nx.draw_networkx_edges(G,pos,ax=ax, node_size=3000, arrowsize=30)

trans=ax.transData.transform
trans2=fig.transFigure.inverted().transform

piesize=0.4 # this is the image size
p2=piesize/2.0
for n in G:
    xx,yy=trans(pos[n]) # figure coordinates
    xa,ya=trans2((xx,yy)) # axes coordinates
    a = plt.axes([xa-p2,ya-p2, piesize, piesize])
    a.set_aspect('equal')
    a.imshow(G.nodes[n]['image'])
    a.axis('off')
ax.axis('off')
plt.show()