1 简介
  均值滤波是一种低通滤波,它可以有效过滤图片中的椒盐噪声,但是副作用也同样明显,会使图片的边缘过于模糊。
   均值滤波的卷积核系数均为1。
   这里最终重复一下算法实现以及验证的步骤:
     1.MATLAB读取图片并转化为TXT格式,命名为pre.txt。
     2.ModelSim读取pre.txt文本并输入给FPGA实现的算法模块进行仿真,并将仿真后的数据写入TXT文本,命名为post.txt。
     3.MATLAB对读取图像并用算法对图像进行处理,同时读取步骤2的post.txt文本进行数据对比,如果数据完全一致,则FPGA算法实现与MALAB算法实现均正确。
     4.MATLAB读取post.txt转化为图片,查看算法实现效果。
   由步骤可知MATLAB共有三个文件,一个图片转TXT,一个算法实现与比较,一个TXT转图片。
2 MATLAB的格式转换
  本试验采用的图片为第六章的RGB转YCBCR最后生成的图片。点击此处跳转到文章,
   转化的MATLAB代码为:
clear;
clc;
close all;
a = imread('../img/gray.bmp');
imshow(a);
[row,col] = size(a);p_fid = fopen('../data/pre.txt','w+');
for i = 1:rowfor j = 1:col fprintf(p_fid,'%02x' ,a(i,j));fprintf(p_fid,'\n');endend
fclose(p_fid);
3 均值滤波的FPGA实现与仿真。
均值滤波要用到3X3的卷积核,这里我们选择边沿复制的方式,卷积核系数均为1,卷积核的生成方式查看第七章点击跳转,在此模块的基础上继续编写均值滤波部分。由于均值滤波需要除以9,在FPGA中的除法实现较为消耗资源与时间,除以9采用先乘以7281再除以65536来实现。
3.1 均值滤波的FPGA实现
3.1.1 3X3卷积核实现
module 	padding_matrix #(parameter 	COL 	= 	1920 	 	,parameter 	ROW 	= 	1080 	 	,parameter 	PADDING = 	0 		 	
)(input 	wire 			clk 		,input 	wire 			rst_n 		,input 	wire 	[7:0] 	data 		,input 	wire 	 		data_de 	, output 	wire  			matrix_de 	,output 	reg 	[7:0] 	matrix11 	,output 	reg 	[7:0] 	matrix12 	,output 	reg 	[7:0] 	matrix13 	,output 	reg 	[7:0] 	matrix21 	,output 	reg 	[7:0] 	matrix22 	,output 	reg 	[7:0] 	matrix23 	,output 	reg 	[7:0] 	matrix31 	,output 	reg 	[7:0] 	matrix32 	,output 	reg 	[7:0] 	matrix33 	
);reg 	[1:0] 	 data_de_r 	;
reg 	[7:0] 	 data_r1 	;
reg 	[7:0] 	 data_r2 	;reg 	[15:0] 	 col_cnt 	;
reg 	[15:0] 	 row_cnt 	;	reg 			data_valid 	;
reg 	[4:0]	data_valid_r;
reg 			fake_data_valid;wire 	[7:0] 	row1_data 	;
wire 	[7:0] 	row2_data 	;
reg 	[7:0] 	row3_data 	;wire  	[1:0] 	padding 	;
assign 	padding  	= 	PADDING;always @(posedge clk )begindata_de_r <= {data_de_r[1:0],data_de};data_valid_r 	<= 	{data_valid_r[3:0],data_valid};data_r1 	<= 	data 		;
end
wire 	pos_data_de;
assign 	pos_data_de = {data_de_r[0],data_de} == 2'b01;always @(posedge clk or negedge rst_n)beginif(rst_n == 0)begincol_cnt 	<= 0;endelse if(col_cnt == COL + 1)begincol_cnt 	<= 0;endelse if(data_valid || fake_data_valid)begincol_cnt 	<= col_cnt + 1;end
endalways @(posedge clk or negedge rst_n)beginif(rst_n == 0)beginrow_cnt 	<= 0;endelse if(col_cnt == COL + 1 && row_cnt == ROW )beginrow_cnt	 	<= 0;endelse if(col_cnt == COL + 1)beginrow_cnt 	<= row_cnt + 1;end
endalways @(posedge clk or negedge rst_n) beginif (rst_n == 0) begin		fake_data_valid 	<= 0;endelse if (data_valid_r[4] == 0 && row_cnt == ROW && col_cnt <= COL  ) beginfake_data_valid 	<= 1;endelse beginfake_data_valid 	<= 	0;end
endalways @(posedge clk or negedge rst_n)beginif(rst_n == 0)beginrow3_data 	<= 0;endelse if(col_cnt == 0 && pos_data_de && padding == 0)beginrow3_data 	<= 0 ;endelse if(col_cnt == 0 && pos_data_de && padding == 1)beginrow3_data 	<= 8'hFF ;endelse if(col_cnt == 0 && pos_data_de)beginrow3_data 	<= data ;endelse if(col_cnt == COL && data_de_r[1] && padding == 0)beginrow3_data 	<= 0;endelse if(col_cnt == COL && data_de_r[1] && padding == 1)beginrow3_data 	<= 8'hFF;endelse if(col_cnt == COL && data_de_r[1])beginrow3_data 	<= row3_data;endelse beginrow3_data 	<= data_r1;end
endalways@(posedge clk or negedge rst_n)beginif(rst_n == 0)begindata_valid <= 0;endelse if(data_de || data_de_r[1])begindata_valid <= 1'b1;endelse begindata_valid <= 1'b0;end
endwire 			rd_en 	;	fifo_matrix_buf u1_fifo_matrix_buf (.rst 		(!rst_n		),  .wr_clk 	(clk  	 	),  .rd_clk 	(clk 	 	),  .din 		(row2_data 	),  .wr_en 		(data_valid ),  .rd_en 		(rd_en 	 	),  .dout 		(row1_data 	),  .full 		( 	 		),  .empty 		( 	 		)   
);fifo_matrix_buf u2_fifo_matrix_buf (.rst 		(!rst_n		),  .wr_clk 	(clk  	 	),  .rd_clk 	(clk 	 	),  .din 		(row3_data 	),  .wr_en 		(data_valid ),  .rd_en 		(rd_en 		),  .dout 		(row2_data 	), .full 		(   		),  .empty 		(    		)   
);assign rd_en = (row_cnt > 0 & (data_valid | fake_data_valid) )? 1'b1 : 1'b0;always @(posedge clk or negedge rst_n)beginif(rst_n == 0)begin{matrix11,matrix12,matrix13} 	<= 	24'd0;{matrix21,matrix22,matrix23} 	<= 	24'd0;{matrix31,matrix32,matrix33} 	<= 	24'd0;endelse if(rd_en)beginif(row_cnt == 1)beginif (padding == 0) begin{matrix11,matrix12,matrix13} 	<= 	{matrix12,matrix13,  	8'h0};{matrix21,matrix22,matrix23} 	<= 	{matrix22,matrix23,row2_data};{matrix31,matrix32,matrix33} 	<= 	{matrix32,matrix33,row3_data};				endif (padding == 1) begin{matrix11,matrix12,matrix13} 	<= 	{matrix12,matrix13,    8'hFF};{matrix21,matrix22,matrix23} 	<= 	{matrix22,matrix23,row2_data};{matrix31,matrix32,matrix33} 	<= 	{matrix32,matrix33,row3_data};				endelse begin{matrix11,matrix12,matrix13} 	<= 	{matrix12,matrix13,row2_data};{matrix21,matrix22,matrix23} 	<= 	{matrix22,matrix23,row2_data};{matrix31,matrix32,matrix33} 	<= 	{matrix32,matrix33,row3_data};				endend	else if (row_cnt == ROW) beginif (padding == 0) begin{matrix11,matrix12,matrix13} 	<= 	{matrix12,matrix13,row1_data};{matrix21,matrix22,matrix23} 	<= 	{matrix22,matrix23,row2_data};{matrix31,matrix32,matrix33} 	<= 	{matrix32,matrix33,     8'h0};				endelse if(padding == 1) begin{matrix11,matrix12,matrix13} 	<= 	{matrix12,matrix13,row1_data};{matrix21,matrix22,matrix23} 	<= 	{matrix22,matrix23,row2_data};{matrix31,matrix32,matrix33} 	<= 	{matrix32,matrix33,    8'hff};				endelse begin{matrix11,matrix12,matrix13} 	<= 	{matrix12,matrix13,row1_data};{matrix21,matrix22,matrix23} 	<= 	{matrix22,matrix23,row2_data};{matrix31,matrix32,matrix33} 	<= 	{matrix32,matrix33,row2_data};				end			endelse begin{matrix11,matrix12,matrix13} 	<= 	{matrix12,matrix13,row1_data};{matrix21,matrix22,matrix23} 	<= 	{matrix22,matrix23,row2_data};{matrix31,matrix32,matrix33} 	<= 	{matrix32,matrix33,row3_data};end	endendreg 	[2:0] 	rd_en_r;
always @(posedge clk)beginrd_en_r 	<= 	{rd_en_r[1:0],rd_en};
endassign 	matrix_de 	= 	rd_en_r[2] & rd_en_r[0] ;
endmodule 	
3.1.2 均值滤波算法的FPGA实现
`timescale 1ns / 1psmodule ave_filter#(parameter DW = 8
)(input   wire                clk         ,input   wire                rst_n       ,input   wire                matrix_de   ,input   wire    [DW-1:0]    matrix11    ,input   wire    [DW-1:0]    matrix12    ,input   wire    [DW-1:0]    matrix13    ,input   wire    [DW-1:0]    matrix21    ,input   wire    [DW-1:0]    matrix22    ,input   wire    [DW-1:0]    matrix23    ,input   wire    [DW-1:0]    matrix31    ,input   wire    [DW-1:0]    matrix32    ,input   wire    [DW-1:0]    matrix33    ,output  wire                ave_data_de ,output  wire    [DW-1:0]    ave_data );reg     [2:0]           matrix_de_r     ;reg     [DW+1:0]        one_line        ;
reg     [DW+1:0]        two_line        ;
reg     [DW+1:0]        three_line      ;
reg     [DW+3:0]        sum_matrix      ;
reg     [DW+15:0]       pre_ave_data    ;always @(posedge clk)beginif(rst_n == 0)beginmatrix_de_r     <=  0;end else beginmatrix_de_r     <=  {matrix_de_r[1:0],matrix_de};end
end always @(posedge clk)beginif(rst_n == 0)beginone_line    <=  0;two_line    <=  0;three_line  <=  0;end else if(matrix_de)beginone_line    <=  matrix11 + matrix12 + matrix13;two_line    <=  matrix21 + matrix22 + matrix23;three_line  <=  matrix31 + matrix32 + matrix33;endelse beginone_line    <=  0;two_line    <=  0;three_line  <=  0;end
endalways @(posedge clk)beginif(rst_n == 0)beginsum_matrix  <=  0;end else if(matrix_de_r[0])beginsum_matrix  <=  one_line + two_line + three_line ;endelse beginsum_matrix  <=  0;end
endalways @(posedge clk)beginif(rst_n == 0)beginpre_ave_data    <=  0;end else if(matrix_de_r[1])beginpre_ave_data    <=  sum_matrix * 7281;endelse beginpre_ave_data    <=  0;end
endassign  ave_data    =   pre_ave_data[DW+15:16];
assign  ave_data_de = matrix_de_r[2];
endmodule
3.1.3 3X3卷积核生成与均值滤波模块的连接
`timescale 1ns / 1ps
module top_ave_filter#(parameter COL       = 1920  ,parameter ROW       = 1080  ,parameter PADDING   = 2     ,parameter DW        = 8     
)(input   wire                clk             ,input   wire                rst_n           ,input   wire                data_de         ,input   wire    [DW-1:0]    data            ,output  wire                ave_data_de     ,output  wire    [DW-1:0]    ave_data          
);wire    [DW-1:0]      matrix11    ;
wire    [DW-1:0]      matrix12    ;
wire    [DW-1:0]      matrix13    ;
wire    [DW-1:0]      matrix21    ;
wire    [DW-1:0]      matrix22    ;
wire    [DW-1:0]      matrix23    ;
wire    [DW-1:0]      matrix31    ;
wire    [DW-1:0]      matrix32    ;
wire    [DW-1:0]      matrix33    ;    padding_matrix #(.COL 	    (COL        ),.ROW 	    (ROW        ),.PADDING    (PADDING    )
)u_padding_matrix(.clk 		    (clk 		    ),.rst_n 		    (rst_n 		    ),.data 		    (data 		    ),.data_de 	    (data_de 	    ), .matrix_de 	    (matrix_de 	    ),.matrix11 	    (matrix11 	    ),.matrix12 	    (matrix12 	    ),.matrix13 	    (matrix13 	    ),.matrix21 	    (matrix21 	    ),.matrix22 	    (matrix22 	    ),.matrix23 	    (matrix23 	    ),.matrix31 	    (matrix31 	    ),.matrix32 	    (matrix32 	    ),.matrix33 	    (matrix33 	    )
);ave_filter #(.DW         (DW)
)u_ave_filter(.clk            (clk            ),.rst_n          (rst_n          ),.matrix_de      (matrix_de      ),.matrix11       (matrix11       ),.matrix12       (matrix12       ),.matrix13       (matrix13       ),.matrix21       (matrix21       ),.matrix22       (matrix22       ),.matrix23       (matrix23       ),.matrix31       (matrix31       ),.matrix32       (matrix32       ),.matrix33       (matrix33       ),.ave_data_de    (ave_data_de    ),.ave_data       (ave_data       ));
endmodule

3.2 FPGA仿真
3.2.1 像素读入
`timescale 1ns / 1psmodule img_gen
#(parameter 	ACTIVE_IW 	= 	1920 	,parameter 	ACTIVE_IH 	= 	1080 	,parameter 	TOTAL_IW 	= 	2200 	,parameter 	TOTAL_IH 	= 	1100 	,parameter 	H_START 	= 	100 	,parameter 	V_START 	= 	4 		 		
)(input 	wire 				clk 	,input 	wire 				rst_n 	,output 	reg 				vs 		,output 	reg  	 	 		de 		,output 	reg 	[7:0] 		data 	
);reg  	[7:0] 	raw_array 	 [ACTIVE_IW*ACTIVE_IH-1:0];integer i;
initial beginfor (i=0 ;i<ACTIVE_IH*ACTIVE_IW ; i=i+1) beginraw_array[i] = 0;end
endinitial begin$readmemh("H:/picture/Z7/lesson7/data/pre.txt",raw_array);
endreg 	[15:0] 	hcnt 	;
reg 	[15:0] 	vcnt 	;reg 			h_de 	;
reg 			v_de  	;reg  			index_de 	;
reg 	[31:0] 	index 	 	;always @(posedge clk or negedge rst_n)if(!rst_n)hcnt <= 'd0;else if(hcnt == TOTAL_IW - 1)hcnt <= 'd0;else hcnt <= hcnt + 1'b1;always @(posedge clk or negedge rst_n)if(!rst_n)vcnt <= 'd0;else if(hcnt == TOTAL_IW - 1 && vcnt == TOTAL_IH - 1)vcnt <= 'd0;else if(hcnt == TOTAL_IW - 1)vcnt <= vcnt + 1'b1;else vcnt <= vcnt;always @(posedge clk or negedge rst_n)if(!rst_n)vs <= 'd0;else if(vcnt>=2)vs <= 1'b1;else vs <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)h_de <= 'd0;else if(hcnt >= H_START && hcnt < H_START + ACTIVE_IW)h_de <= 1'b1;else h_de <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)v_de <= 'd0;else if(vcnt >= V_START && vcnt < V_START + ACTIVE_IH)v_de <= 1'b1;else v_de <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)index_de <= 'd0;else if(h_de == 1'b1 && v_de == 1'b1)index_de <= 1'b1;else index_de <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)index <= 'd0;else if(index == ACTIVE_IW * ACTIVE_IH-1)index <= 0;else if(index_de == 1'b1)index <= index + 1;else index <= index;always @(posedge clk or negedge rst_n)if(!rst_n)de <= 'd0;else de <= index_de;always @(posedge clk or negedge rst_n)beginif(index_de == 1'b1)data 	<= 	raw_array[index];else data 	<= 0;
end
endmodule
3.2.1 顶层TB连接
`timescale 1ns / 1psmodule img_gen
#(parameter 	ACTIVE_IW 	= 	1920 	,parameter 	ACTIVE_IH 	= 	1080 	,parameter 	TOTAL_IW 	= 	2200 	,parameter 	TOTAL_IH 	= 	1100 	,parameter 	H_START 	= 	100 	,parameter 	V_START 	= 	4 		 		
)(input 	wire 				clk 	,input 	wire 				rst_n 	,output 	reg 				vs 		,output 	reg  	 	 		de 		,output 	reg 	[7:0] 		data 	
);reg  	[7:0] 	raw_array 	 [ACTIVE_IW*ACTIVE_IH-1:0];integer i;
initial beginfor (i=0 ;i<ACTIVE_IH*ACTIVE_IW ; i=i+1) beginraw_array[i] = 0;end
endinitial begin$readmemh("H:/picture/Z7/lesson7/data/pre.txt",raw_array);
endreg 	[15:0] 	hcnt 	;
reg 	[15:0] 	vcnt 	;reg 			h_de 	;
reg 			v_de  	;reg  			index_de 	;
reg 	[31:0] 	index 	 	;always @(posedge clk or negedge rst_n)if(!rst_n)hcnt <= 'd0;else if(hcnt == TOTAL_IW - 1)hcnt <= 'd0;else hcnt <= hcnt + 1'b1;always @(posedge clk or negedge rst_n)if(!rst_n)vcnt <= 'd0;else if(hcnt == TOTAL_IW - 1 && vcnt == TOTAL_IH - 1)vcnt <= 'd0;else if(hcnt == TOTAL_IW - 1)vcnt <= vcnt + 1'b1;else vcnt <= vcnt;always @(posedge clk or negedge rst_n)if(!rst_n)vs <= 'd0;else if(vcnt>=2)vs <= 1'b1;else vs <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)h_de <= 'd0;else if(hcnt >= H_START && hcnt < H_START + ACTIVE_IW)h_de <= 1'b1;else h_de <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)v_de <= 'd0;else if(vcnt >= V_START && vcnt < V_START + ACTIVE_IH)v_de <= 1'b1;else v_de <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)index_de <= 'd0;else if(h_de == 1'b1 && v_de == 1'b1)index_de <= 1'b1;else index_de <= 1'b0;always @(posedge clk or negedge rst_n)if(!rst_n)index <= 'd0;else if(index == ACTIVE_IW * ACTIVE_IH-1)index <= 0;else if(index_de == 1'b1)index <= index + 1;else index <= index;always @(posedge clk or negedge rst_n)if(!rst_n)de <= 'd0;else de <= index_de;always @(posedge clk or negedge rst_n)beginif(index_de == 1'b1)data 	<= 	raw_array[index];else data 	<= 0;
end
endmodule
4 MATLAB实现与比较
4.1 MATLAB实现
clc;
clear all;
GRAY = imread('../img/gray.bmp');
[row,col] = size(GRAY);
GRAY = double(GRAY);
ave_padding = zeros(row+2,col+2);
ave_result  =   zeros(row,col);
for i = 1:rowfor j = 1:colave_padding(i+1,j+1) = GRAY(i,j);end
endfor i = 1:row+2ave_padding(i,1) = ave_padding(i,2);ave_padding(i,col+2) = ave_padding(i,col+1);
endfor i = 1:col+2ave_padding(1,i) = ave_padding(2,i);ave_padding(row+2,i) = ave_padding(row+1,i);
endfor i = 2:row+1for j = 2:col+1matrix11 = ave_padding(i-1,j-1);matrix12 = ave_padding(i-1,j);matrix13 = ave_padding(i-1,j+1);matrix21 = ave_padding(i,j-1);matrix22 = ave_padding(i,j);matrix23 = ave_padding(i,j+1);matrix31 = ave_padding(i+1,j-1);matrix32 = ave_padding(i+1,j);matrix33 = ave_padding(i+1,j+1); ave_result(i-1,j-1) = (matrix11+matrix12+matrix13+matrix21+matrix22+matrix23+matrix31+matrix32+matrix33)/9;end
end
matlab_Y = uint8(floor(ave_result));a = textread('../data/post.txt','%s');
IMdec = hex2dec(a);col = 1920;
row = 1080;IM = reshape(IMdec,col,row);
fpga_Y = uint8(IM)';subplot(1,2,1)
imshow(matlab_Y),title('MATLAB算法图像');
subplot(1,2,2)
imshow(fpga_Y),title('FPGA算法图像');sub = matlab_Y - fpga_Y;min_sub = min(min(sub));
max_sub = max(max(sub));4.2 比较
4.2.1 数据比较

   两者实现像素做差可以看出FPGA实现与MATLAB实现在部分像素区域有着一个像素点的误差,这在定浮点数中无可避免。
4.2.2 算法结果比较

4.2.3算法前后比较
将FPGA仿真得到的post.txt图像数据转化为BMP格式的图片并显示出来。转化代码为:
clear ;
clc ;
close;
a = textread("../data/post.txt",'%s');
IMdec = hex2dec(a);col = 1920;
row = 1080;IM = reshape(IMdec,col,row);
b = uint8(IM)';
imwrite(b,'../img/post.bmp');
subplot(1,2,1)
imshow('../img/post.bmp'),title('FPGA算法图像');
subplot(1,2,2)
imshow('../img/gray.bmp'),title('原图像');
  得到的图像对比如下图,可以看出边缘明显变模糊,这也是均值滤波的缺点,所以一般情况下不会用均值滤波来做图像处理,一般采用中值滤波等。
 