如何使用 T-SQL 将十六进制颜色转换为 RGB 颜色 [英] How do I convert a Hex color to and RGB color using T-SQL

问题描述

如何使用 T-SQL 将十六进制颜色转换为 RGB 颜色

How do I convert a Hex color to and RGB color using T-SQL

推荐答案

https://data.stackexchange.com/stackoverflow/query/4803/so3087921

DECLARE @temp AS TABLE (hex char(6))

INSERT  INTO @temp
VALUES  ('3333CC') -- Should convert to Red: 51 Green: 51 Blue: 204

DECLARE @table AS varchar(16)
SET @table = '0123456789abcdef' -- Assuming case-insensitive collation!

SELECT  hex
       ,16 * (CHARINDEX(SUBSTRING(hex, 1, 1), @table) - 1) + (CHARINDEX(SUBSTRING(hex, 2, 1), @table) - 1) AS R
       ,16 * (CHARINDEX(SUBSTRING(hex, 3, 1), @table) - 1) + (CHARINDEX(SUBSTRING(hex, 4, 1), @table) - 1) AS G
       ,16 * (CHARINDEX(SUBSTRING(hex, 5, 1), @table) - 1) + (CHARINDEX(SUBSTRING(hex, 6, 1), @table) - 1) AS B
FROM    @temp

https://dpatrickcaldwell.blogspot.com/2009/05/converting-hexadecimal-or-binary-to.html

如果可能，我通常会尽量避免使用标量函数，因为可能会诱使自己认为可以为 500 万行调用标量 UDF，而不会对内联表达式造成任何损失.

I generally avoid scalar functions if at all possible, since it is possible to lure yourself into thinking that it's OK to call a scalar UDF for 5 million rows without any penalty over the inline expression.

您还可以使用内联表值 UDF:

You can also use an inline table-valued UDF:

CREATE FUNCTION dbo.udf_HexToRGB (@hex char(6))
RETURNS TABLE
AS RETURN
    (
     SELECT 16 * (CHARINDEX(SUBSTRING(@hex, 1, 1), '0123456789abcdef') - 1) + (CHARINDEX(SUBSTRING(@hex, 2, 1),
                                                                                         '0123456789abcdef') - 1) AS R
           ,16 * (CHARINDEX(SUBSTRING(@hex, 3, 1), '0123456789abcdef') - 1) + (CHARINDEX(SUBSTRING(@hex, 4, 1),
                                                                                         '0123456789abcdef') - 1) AS G
           ,16 * (CHARINDEX(SUBSTRING(@hex, 5, 1), '0123456789abcdef') - 1) + (CHARINDEX(SUBSTRING(@hex, 6, 1),
                                                                                         '0123456789abcdef') - 1) AS B
    )
GO

DECLARE @temp AS TABLE (hex char(6)) 

INSERT  INTO @temp 
VALUES  ('3333CC') -- Should convert to Red: 51 Green: 51 Blue: 204 

SELECT  hex 
       ,R 
       ,G 
       ,B 
FROM    @temp
OUTER APPLY dbo.udf_HexToRGB(hex)

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