获取raster对象的某一个波段的颜色表信息，返回颜色表的JSON格式。
语法
text ST_ColorTable(raster raster_obj, integer band);
参数
| 参数名称 | 描述 |
|---|---|
| raster_obj | raster对象。 |
| band | 指定的波段序号，从0开始。 |
描述
颜色表的JSON格式：
- 4分量：
'{"compsCount":4, "entries":[ {"value":0,"c1":0,"c2":0,"c3":0,"c4":255}, {"value":1,"c1":0,"c2":0,"c3":85,"c4":255}, {"value":2,"c1":0,"c2":0,"c3":170,"c4":255} ] }' - 3分量：
'{"compsCount":3, "entries":[ {"value":0,"c1":0,"c2":0,"c3":0}, {"value":1,"c1":0,"c2":0,"c3":85}, {"value":2,"c1":0,"c2":0,"c3":170} ] }'
如果不存在颜色表，函数返回空值。
示例
select ST_ColorTable(raster_obj,0) from raster_table where id = 1;
__________________________________
'{"compsCount":3,
"entries":
[
{"value":0,"c1":0,"c2":0,"c3":0},
{"value":1,"c1":0,"c2":0,"c3":85},
{"value":2,"c1":0,"c2":0,"c3":170}
]
}'
