无法将鼠标单击中的x，y坐标转换为装配体中的像素颜色

Question

我用2个proc创建了非常简短的代码，应该通过单击鼠标来获取坐标，然后在该像素的精确坐标中打印颜色。

我似乎找不到问题所在。无论在哪里单击，它都会打印0。

Create Role Sales_Person
    Grant Insert on Northwind.dbo.Customers 
    To Sales_Person
    Grant Insert on Northwind.dbo.Orders
    To Sales_Person
    Grant Insert on Northwind.dbo.OrderDetails
    To Sales_Person
    Grant Select, Update on Northwind.dbo.Customers(CompanyName, ContactName, ContactTitle, Address, City, Region, PostalCode, Country, Phone, Fax)
    To Sales_Person
Create Role Sale_Manager
    Grant Insert, Delete on Northwind.dbo.Customers
    To Sale_Manager
    Grant Insert, Delete on Northwind.dbo.Orders
    To Sale_Manager
    Grant Insert, Delete on Northwind.dbo.OrderDetails
    To Sale_Manager
    Grant Select, Update on Northwind.dbo.Customers(CompanyName, ContactName, ContactTitle, Address, City, Region, PostalCode, Country, Phone, Fax)
    To Sale_Manager
Create Role HR_Person
    Grant Insert on Northwind.dbo.Employees
    To HR_Person
    Grant Select, Update on Northwind.dbo.Employees(LastName, FirstName, Title, TitleOfCourtesy, BirthDate, HireDate, Address, City, Region, PostalCode, HomePhone, Country, Extension, Notes, ReportTo)
    To HR_Person
Create Role HR_Manager
    Grant Insert, Delete on Northwind.dbo.Employees
    To HR_Manager
    Grant Select, Update on Northwind.dbo.Employees(LastName, FirstName, Title, TitleOfCourtesy, BirthDate, HireDate, Address, City, Region, PostalCode, HomePhone, Country, Extension, Notes, ReportTo)
    To HR_Manager
Create User Jane1 Without Login
    Grant Sales_Person to Jane1
Create User Joan1 Without Login
    Grant Sale_Manager to Joan1
Create User Joe1 Without Login
    Grant HR_Person to Joe1
Create User James1 Without Login

应该打印的是4（从一开始的色号），但是它一直打印0 ...为什么？代码有什么问题？