The Custom Renderer output images contain nothing

Hello,

When I use the Custom Renderer feature,it rendered an image which only contained some black and white lines
Like this:

My console output some warnings:

warning: unused import: `WriteBytesExt`
--> src/buf_rw.rs:3:42
|
3 | use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
| ^^^^^^^^^^^^^
|
= note: `#[warn(unused_imports)]` on by default

warning: trait objects without an explicit `dyn` are deprecated
--> src/colorizer.rs:178:46
|
178 | pub fn get_column_color_fn(&self) -> Box u32> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn Fn(&[u8], &KeysMap, &NamesVec) -> u32`
|
= note: `#[warn(bare_trait_objects)]` on by default

warning: use of deprecated item 'std::error::Error::description': use the Display impl or to_string()
--> src/buf_rw.rs:7:1
|
7 | / error_chain!{
8 | | types {
9 | | BufErr, BufErrorKind, BufResult;
10 | | }
... |
15 | | }
16 | | }
| |_^
|
= note: `#[warn(deprecated)]` on by default
= note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

warning: use of deprecated item 'std::error::Error::description': use the Display impl or to_string()
--> src/buf_rw.rs:7:1
|
7 | / error_chain!{
8 | | types {
9 | | BufErr, BufErrorKind, BufResult;
10 | | }
... |
15 | | }
16 | | }
| |_^
|
= note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

warning: use of deprecated item 'std::error::Error::description': use the Display impl or to_string()
--> src/replay.rs:12:1
|
12 | / error_chain!{
13 | | types {
14 | | ReplayErr, ReplayErrorKind, ReplayResult;
15 | | }
... |
20 | | }
21 | | }
| |_^
|
= note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

warning: unused import: `Write`
--> src/buf_rw.rs:5:29
|
5 | use std::io::{Cursor, Read, Write};
| ^^^^^

warning: constant `unknown_biome_name` should have an upper case name
--> src/biomes.rs:297:7
|
297 | const unknown_biome_name: &'static str = "?UNKNOWN_BIOME?";
| ^^^^^^^^^^^^^^^^^^ help: convert the identifier to upper case: `UNKNOWN_BIOME_NAME`
|
= note: `#[warn(non_upper_case_globals)]` on by default

My platform:
Raspbian GNU/Linux 10
Python 3.7.3
Pillow 7.1.1
rustup 1.21.1 (7832b2ebe 2019-12-20)

How can I fix this problem?