如何在FPGA中实现RGB转HSV

HSV色彩空间相对于RGB色彩空间更适合做颜色追踪，分割颜色等。那么RGB色彩空间要怎么转变为HSV色彩空间呢。

转换公式如下：

需要注意的是在OpenCV中为了显示HSV色彩空间的内容会将H的值除以2，S的值和V的值是要乘以255。

在FPGA中实现RGB转HSV的话，上面公式中第一步除以255的归一化是可以不做的。因为在H和S的计算中255可以约掉的，如下所示。而在V的值需要乘以255来显示，所以也可以不除以255.

如R,G,B为169 152 133的值计算过程如下：

定义如下

在计算中需要使用除法器：

因为8bit的整数，8bit小数的有符号数，所以数据位宽为17bit。

仿真结果如下：

可以看到ref和dut之间有误差，这个是因为计算过程中采用了8bit的定点小数造成的，如果小数位宽扩大，那么可以减少误差。

仿真用的计分板：

提供SpinalHDL的源码：如果需要Verilog源码可以私聊

import spinal.core._
import spinal.lib._


class Rgb2hsv extends Component {
    val io = new Bundle {
        val dataIn = slave(FrameInterface(24))
        val dataOut = master(FrameInterface(24))
    }


    val R, G, B = UInt(8 bits)
    val RMax = Reg(Bool()) init False
    val GMax = Reg(Bool()) init False
    val BMax = Reg(Bool()) init False
    val RMaxDelay = Delay(RMax, 12, init = False)
    val GMaxDelay = Delay(GMax, 12, init = False)
    val BMaxDelay = Delay(BMax, 12, init = False)
    val CMax = Reg(UInt(8 bits))
    val CMin = Reg(UInt(8 bits))
    val derta = UInt(8 bits)


    val calcH = new Area {
        val dertaEq0 = Delay(derta === 0, 12)
        val G_B = RegNext(((U"1'b0" @@ G).asSInt - (U"1'b0" @@ B).asSInt) @@ S"8'd0")
        val B_R = RegNext(((U"1'b0" @@ B).asSInt - (U"1'b0" @@ R).asSInt) @@ S"8'd0")
        val R_G = RegNext(((U"1'b0" @@ R).asSInt - (U"1'b0" @@ G).asSInt) @@ S"8'd0")
        val div1 = new Div(17, 8)
        val div2 = new Div(17, 8)
        val div3 = new Div(17, 8)
        val G_B_derta = Bits(17 bits)
        val B_R_derta = Bits(17 bits)
        val R_G_derta = Bits(17 bits)
        val G_B_derta_add = Reg(SInt(17 bits))
        val B_R_derta_add = Reg(SInt(17 bits))
        val R_G_derta_add = Reg(SInt(17 bits))
        val G_B_derta_add_mul = Reg(SInt(16 bits))
        val B_R_derta_add_mul = Reg(SInt(16 bits))
        val R_G_derta_add_mul = Reg(SInt(16 bits))
        val H_D = Reg(UInt(9 bits))
        val H = Reg(UInt(8 bits))
        div1.driverFrom(G_B.asBits, (U"1'b0" @@ derta @@ U"8'b0").asBits, RMax, G_B_derta)
        div2.driverFrom(B_R.asBits, (U"1'b0" @@ derta @@ U"8'b0").asBits, GMax, B_R_derta)
        div3.driverFrom(R_G.asBits, (U"1'b0" @@ derta @@ U"8'b0").asBits, BMax, R_G_derta)


        G_B_derta_add := G_B_derta.asSInt
        B_R_derta_add := B_R_derta.asSInt + 2 @@ S"8'b0"
        R_G_derta_add := R_G_derta.asSInt + 4 @@ S"8'b0"


        val mul60 = AFix.S(8 exp, -8 exp)
        val afixG_B_derta_add = AFix.S(8 exp, -8 exp)
        val afixB_R_derta_add = AFix.S(8 exp, -8 exp)
        val afixR_G_derta_add = AFix.S(8 exp, -8 exp)
        afixG_B_derta_add := G_B_derta_add
        afixB_R_derta_add := B_R_derta_add
        afixR_G_derta_add := R_G_derta_add
        mul60 := S"9'd60" @@ S"8'd0"
        G_B_derta_add_mul := (mul60 * afixG_B_derta_add).roundHalfUp(0).asSInt().resized
        B_R_derta_add_mul := (mul60 * afixB_R_derta_add).roundHalfUp(0).asSInt().resized
        R_G_derta_add_mul := (mul60 * afixR_G_derta_add).roundHalfUp(0).asSInt().resized


        //  val H = SInt(9 bits)
        (R, G, B) := io.dataIn.data
        when(R >= G && R >= B) {
            CMax := R
            RMax := True
            GMax := False
            BMax := False
        } elsewhen (G >= R && G >= B) {
            CMax := G
            RMax := False
            GMax := True
            BMax := False
        } otherwise {
            CMax := B
            RMax := False
            GMax := False
            BMax := True
        }


        when(R <= G && R <= B) {
            CMin := R
        } elsewhen (G <= R && G <= B) {
            CMin := G
        } otherwise {
            CMin := B
        }
        derta := CMax - CMin


        when(dertaEq0) {
            H_D := 0
        } elsewhen (RMaxDelay) {
            when(G_B_derta_add_mul.sign) {
                H_D := (G_B_derta_add_mul +^ 360).asUInt.resized
            } otherwise {
                H_D := G_B_derta_add_mul(8 downto 0).asUInt.resized
            }


        } elsewhen (GMaxDelay) {
            when(B_R_derta_add_mul.sign) {
                H_D := (B_R_derta_add_mul + 360).asUInt.resized
            } otherwise {
                H_D := B_R_derta_add_mul(8 downto 0).asUInt.resized
            }
        } elsewhen (BMaxDelay) {
            when(R_G_derta_add_mul.sign) {
                H_D := (R_G_derta_add_mul + 360).asUInt.resized
            } otherwise {
                H_D := R_G_derta_add_mul(8 downto 0).asUInt.resized
            }
        }
        H := (H_D(8 downto 1) + H_D(0).asUInt)


    }


    val calcS = new Area {
        val S_Div = Bits(17 bits)
        val div = new Div(17, 8)
        div.driverFrom((U"1'd0" @@ derta @@ U"8'd0").asBits, (U"1'd0" @@ CMax @@ U"8'd0").asBits, RegNext(io.dataIn.valid), S_Div)
        val mul255 = AFix.S(8 exp, -8 exp)
        val afixS = AFix.S(8 exp, -8 exp)
        afixS := S_Div.asSInt
        mul255 := S"9'd255" @@ S"8'd0"
        val afix_mul = RegNext(afixS * mul255)
        val afix_mul_r = RegNext(RegNext(afix_mul.roundHalfUp(0)).asUInt())
        val S = Reg(UInt(8 bits))
        val CMaxEq0 = Delay(CMax === 0, 13)
        when(CMaxEq0){
            S := 0
        } otherwise{
            S := afix_mul_r(7 downto 0)
        }
    }


    val calcV = new Area {
        val V = Delay(CMax, 14)
    }


    io.dataOut.valid := Delay(io.dataIn.valid, 15, init = False)
    io.dataOut.data := (calcH.H @@ calcS.S @@ calcV.V).asBits


}


object Rgb2hsv extends App {
    SpinalVerilog(new Rgb2hsv)
}

审核编辑：汤梓红