uv-palette.py

bl_info = {
    "name": "UV Palette",
    "author": "aarthificial",
    "version": (1, 0),
    "blender": (3, 6, 0),
    "location": "View3D > Object",
    "description": "Modifies the UV to fit a palette.",
    "category": "Object",
}

import bpy

def modify_uv(obj, texture, material):
    bpy.context.view_layer.objects.active = obj
    bpy.ops.object.mode_set(mode='EDIT')
    bpy.ops.mesh.select_all(action='SELECT')
    bpy.ops.uv.reset()
    bpy.ops.object.mode_set(mode='OBJECT')

    uv_map = obj.data.uv_layers["UVMap"]
    for index in range(len(uv_map.data)):
        uv = uv_map.data[index].uv
        uv.x /= 2 * texture
        uv.y /= 2 * texture
        uv.y += 1 - (0.75 / texture)
        uv.x += (material + 0.25) / texture

def custom_context_menu(self, context):
    layout = self.layout
    layout.separator()
    layout.operator_context = "INVOKE_DEFAULT"
    layout.operator("object.custom_operator", text="Apply UV Palette")

class CustomOperator(bpy.types.Operator):
    bl_idname = "object.custom_operator"
    bl_label = "UV Palette Operator"

    material_prop: bpy.props.IntProperty(name="Material index", default=0)
    size_prop: bpy.props.IntProperty(name="Texture size", default=32)

    def execute(self, context):
        for obj in bpy.context.selected_objects:
            if obj and obj.type == 'MESH':
                modify_uv(obj, self.size_prop, self.material_prop)
        return {'FINISHED'}

    def invoke(self, context, event):
        return context.window_manager.invoke_props_dialog(self)

def register():
    bpy.utils.register_class(CustomOperator)
    bpy.types.VIEW3D_MT_object_context_menu.append(custom_context_menu)

def unregister():
    bpy.utils.unregister_class(CustomOperator)
    bpy.types.VIEW3D_MT_object_context_menu.remove(custom_context_menu)

if __name__ == "__main__":
    register()