【数字图像处理】水平翻转、垂直翻转

图像翻转是常见的数字图像处理方式，分为水平翻转和垂直翻转。本文主要介绍 FPGA 实现图像翻转的基本思路，以及使用紫光同创 PGL22G 开发板实现数字图像水平翻转、垂直翻转的过程。

1 水平翻转与垂直翻转

2 FPGA 布署与实现

2.1 功能与指标定义

2.2 逻辑设计

2.3 上板调试

1 水平翻转与垂直翻转

在数字图像处理中，图像翻转是指将图像进行水平或者垂直方向的翻转，使其呈现不同的效果，分为水平翻转和垂直翻转。

水平翻转是将图像沿着水平轴线进行翻转，将左半部分和右半部分进行交换。垂直翻转则是将图像沿着垂直轴线进行翻转，将上部分和下部分进行交换。

使用 FPGA 实现水平翻转时，由于每次向 DDR3 写入一行数据，因此可以借助写 DDR3 之前的 Dual-port RAM，将一行数据进行翻转，实现水平翻转的功能。FPGA 逻辑设计的大致思路是：写 Dual-port RAM 时，写地址从 0 增加；读 Dual-port RAM 写 DDR3 时，读地址从最大值逐步减小到 0 结束。

对于垂直翻转功能，则需要借助 DDR3 来实现。像素数据第 1 行写到第 N 行的位置，第 2 行写到第 N-1 行的位置，以此类推。FPGA 逻辑设计的大致思路是：每一行数据写入 DDR3 时，用图像高度减去原来的行地址，作为新的行地址。

2 FPGA 布署与实现

2.1 功能与指标定义

使用紫光同创 FPGA 平台实现图像翻转功能，FPGA 需要实现的功能与指标如下：

（1）与电脑的串口通信，用于接收上位机下发的图像数据，波特率为 256000 Bd/s；

（2）水平翻转与图像翻转：借助 Dual-port RAM 与 DDR3，分别实现水平翻转与垂直翻转功能；

（3）DDR3 读写控制，将处理前后的图像数据分别写入 DDR3 的不同区域，实现图像的拼接；

（4）HDMI 输出，输出一路 HDMI 信号源，用于将拼接后的图像显示在外接显示器上，分辨率为 1024×768。

2.2 逻辑设计

图像翻转工程主要的设计模块层次与功能说明如下：

模块名称		功能说明
top_uart	uart_rx_slice	串口接收驱动模块
top_uart	uart_rx_parse	串口数据解析模块，从上位机接收 8bit 原始图像
top_vidin	vidin_pipeline	pipeline 单元模块，缓存两行图像数据，并将数据提交到 ddr3 数据调度模块
merge_out	dvi_timing_gen	HDMI 视频时序产生模块
	dvi_ddr_rd	根据 HDMI 控制信号，提交读指令到 ddr3 数据调度模块
	dvi_encoder	HDMI 输出编码（8b10b 编码）与输出驱动模块

其中，vidin_pipeline 模块实现图像翻转功能，代码如下：

`timescale 1 ns/ 1 ps`include "../ddr_scheduler/ddr_parameter.vh"module vidin_pipeline (// System levelsys_rst,sys_clk,ddr_init_done,flip_lr,flip_ud,// pipeline input portspipeline_in_info,pipeline_in_data,pipeline_in_wren,pipeline_in_end,// pipeline output portspipeline_out_info,pipeline_out_data,pipeline_out_vld,pipeline_out_end,// User defined ports for ddr_schedulerddr_wr_baseaddr,ddr_wr_addr,ddr_wr_priority,ddr_wr_burstsize,ddr_wr_req,ddr_wr_ack,ddr_wr_end,ddr_wr_rden,ddr_wr_q,ddr_wr_mask
);// IO direction/register definitions
input                     sys_rst;
input                     sys_clk;
input                     ddr_init_done;
input                     flip_lr;
input                     flip_ud;input  [31:0]             pipeline_in_info;
input  [31:0]             pipeline_in_data;
input                     pipeline_in_wren;
input                     pipeline_in_end;output [31:0]             pipeline_out_info;
output [31:0]             pipeline_out_data;
output                    pipeline_out_vld;
output                    pipeline_out_end;input  [`DDR_A_W-1:0]     ddr_wr_baseaddr;
output [`DDR_A_W-1:0]     ddr_wr_addr;
output                    ddr_wr_priority;
output [`DDR_BURST_W-1:0] ddr_wr_burstsize;
output                    ddr_wr_req;
input                     ddr_wr_ack;
input                     ddr_wr_end;
input                     ddr_wr_rden;
output [`DDR_D_W-1:0]     ddr_wr_q;
output [`DDR_D_W/8-1:0]   ddr_wr_mask;reg    [31:0]             pipeline_out_info;
reg    [31:0]             pipeline_out_data;
reg                       pipeline_out_vld;
reg                       pipeline_out_end;// internal signal declarations
reg    [`DDR_CMD_W-1:0]   ddr_cmd_data;
reg                       ddr_cmd_vld;reg    [9:0]              blk_mem_waddr;
reg    [31:0]             blk_mem_wdata;
reg                       blk_mem_wren;
reg    [9:0]              blk_mem_raddr;
wire   [31:0]             blk_mem_rdata;
reg                       blk_mem_rden;
reg                       blk_mem_rd_busy;
reg                       blk_mem_rd_end;
reg                       blk_mem_rd_vld;// line_buffer_inst: Dual-port ram for line pixel data buffer
blk_mem_1024x32b line_buffer_inst (.wr_data         (blk_mem_wdata   ), // input 32-bit.wr_addr         (blk_mem_waddr   ), // input 10-bit.wr_en           (blk_mem_wren    ), // input 1-bit.wr_clk          (sys_clk         ), // input 1-bit.wr_rst          (sys_rst         ), // input 1-bit.rd_addr         (blk_mem_raddr   ), // input 10-bit.rd_data         (blk_mem_rdata   ), // output 32-bit.rd_clk          (sys_clk         ), // input 1-bit.rd_rst          (sys_rst         )  // input 1-bit
);
// End of line_buffer_inst instantiationalways @(posedge sys_rst or posedge sys_clk) beginif (sys_rst) beginblk_mem_waddr <= {10{1'b0}};blk_mem_wdata <= {32{1'b0}};blk_mem_wren  <= 1'b0;endelse beginblk_mem_wdata <= pipeline_in_data;blk_mem_wren  <= pipeline_in_wren;// Use ping-pong storage hereif (pipeline_in_end) blk_mem_waddr <= {~blk_mem_waddr[9], {9{1'b0}}};else if (pipeline_in_wren) blk_mem_waddr <= {blk_mem_waddr[9], blk_mem_waddr[0+:9]+1'b1};end
endalways @(posedge sys_rst or posedge sys_clk) beginif (sys_rst) beginblk_mem_raddr   <= {10{1'b0}};blk_mem_rden    <= 1'b0;blk_mem_rd_busy <= 1'b0;blk_mem_rd_end  <= 1'b0;blk_mem_rd_vld  <= 1'b0;endelse beginif (~blk_mem_rd_busy && pipeline_in_end) beginblk_mem_rd_busy <= 1'b1;if (flip_lr == 1'b0) blk_mem_raddr <= {blk_mem_raddr[9], {9{1'b0}}};elseblk_mem_raddr <= {blk_mem_raddr[9], {9{1'b1}}};endelse if (blk_mem_rd_busy) begin// Use ping-pong storage hereif (flip_lr == 1'b0) beginif (& blk_mem_raddr[0+:9]) blk_mem_raddr <= {~blk_mem_raddr[9], {9{1'b0}}};else blk_mem_raddr <= {blk_mem_raddr[9], blk_mem_raddr[0+:9]+1'b1};endelse beginif (blk_mem_raddr[0+:9] == 0)blk_mem_raddr <= {~blk_mem_raddr[9], {9{1'b1}}};elseblk_mem_raddr <= {blk_mem_raddr[9], blk_mem_raddr[0+:9]-1'b1};end// Pull down read busy flagif (flip_lr == 1'b0) beginif (& blk_mem_raddr[0+:9]) blk_mem_rd_busy <= 1'b0;endelse beginif (blk_mem_raddr[0+:9] == 0)blk_mem_rd_busy <= 1'b0;endendblk_mem_rden <= blk_mem_rd_busy;blk_mem_rd_vld <= blk_mem_rden;if (blk_mem_rd_busy) beginif (flip_lr == 1'b0) beginif (& blk_mem_raddr[0+:9]) blk_mem_rd_end <= 1'b1;else blk_mem_rd_end <= 1'b0;endelse beginif (blk_mem_raddr[0+:9] == 0)blk_mem_rd_end <= 1'b1;else blk_mem_rd_end <= 1'b0;endendelseblk_mem_rd_end <= 1'b0;end
endalways @(posedge sys_rst or posedge sys_clk) beginif (sys_rst) beginpipeline_out_info <= {32{1'b0}};pipeline_out_data <= {32{1'b0}};pipeline_out_vld  <= 1'b0;pipeline_out_end  <= 1'b0;endelse beginif (pipeline_in_end) pipeline_out_info <= pipeline_in_info;pipeline_out_data <= blk_mem_rdata;pipeline_out_vld  <= blk_mem_rd_vld;pipeline_out_end  <= blk_mem_rd_end;end
end/
always @(posedge sys_rst or posedge sys_clk) beginif (sys_rst) beginddr_cmd_data <= {`DDR_CMD_W{1'b0}};ddr_cmd_vld <= 1'b0;endelse beginif (pipeline_in_end) beginddr_cmd_data[32+:`DDR_BURST_W] <= 8'h7F; // used fixed size here, 512 /4 -1 = 127if (flip_ud == 1'b0)ddr_cmd_data[0+:28] <= {pipeline_in_info[0+:16], 12'd0};elseddr_cmd_data[0+:28] <= {16'd383-pipeline_in_info[0+:16], 12'd0};endif (blk_mem_rd_end) ddr_cmd_vld <= 1'b1;else ddr_cmd_vld <= 1'b0;end
end// vid_ddr_wr_inst: ddr write control module
vid_ddr_wr vid_ddr_wr_inst (.sys_rst          (sys_rst           ), // input 1-bit.sys_clk          (sys_clk           ), // input 1-bit.ddr_init_done    (ddr_init_done     ), // input 1-bit.vid_cmd_data     (ddr_cmd_data      ), // input 40-bit.vid_cmd_vld      (ddr_cmd_vld       ), // input 1-bit.vid_img_data     (blk_mem_rdata     ), // input 32-bit.vid_img_data_vld (blk_mem_rd_vld    ), // input 1-bit.ddr_wr_baseaddr  (ddr_wr_baseaddr   ), // input 27-bit.ddr_wr_addr      (ddr_wr_addr       ), // output 27-bit.ddr_wr_priority  (ddr_wr_priority   ), // output 1-bit.ddr_wr_burstsize (ddr_wr_burstsize  ), // output 8-bit.ddr_wr_req       (ddr_wr_req        ), // output 1-bit.ddr_wr_ack       (ddr_wr_ack        ), // input 1-bit.ddr_wr_end       (ddr_wr_end        ), // input 1-bit.ddr_wr_rden      (ddr_wr_rden       ), // input 1-bit.ddr_wr_q         (ddr_wr_q          ), // output 128-bit.ddr_wr_mask      (ddr_wr_mask       )  // output 16-bit
);
// End of vid_ddr_wr_inst instantiationendmodule

2.3 上板调试

使用 PyQt5 和 OpenCV 库编写上位机程序，通过串口发送原始图像数据，以及水平翻转、垂直翻转参数。

# -*- Coding: UTF-8 -*-
import cv2
import sys
import struct
import numpy as np
from PyQt5 import Qt, QtGui, QtCore, QtWidgets, QtSerialPortclass mainWindow(Qt.QWidget):def __init__(self, com_port, parent=None):super(mainWindow, self).__init__(parent)self.setFixedSize(530, 384)self.setWindowTitle("PGL OpenCV Tool")self.flip_horizontal = Falseself.flip_vertical = False# 创建标签与按钮self.img_widget = QtWidgets.QLabel()self.btn1 = QtWidgets.QPushButton("打开")self.btn1.clicked.connect(self.getfile)self.btn2 = QtWidgets.QPushButton("关闭")self.btn2.clicked.connect(self.close)self.btn3 = QtWidgets.QPushButton("水平翻转")self.btn3.clicked.connect(self.flip_lr)self.btn4 = QtWidgets.QPushButton("垂直翻转")self.btn4.clicked.connect(self.flip_ud)# 创建布局centralLayout = QtWidgets.QVBoxLayout()centralLayout.addWidget(self.img_widget)bottomLayout = QtWidgets.QHBoxLayout()bottomLayout.addWidget(self.btn1)bottomLayout.addWidget(self.btn2)bottomLayout.addWidget(self.btn3)bottomLayout.addWidget(self.btn4)centralLayout.addLayout(bottomLayout)self.setLayout(centralLayout)# 串口对象self.COM = QtSerialPort.QSerialPort()self.COM.setPortName(com_port)self.COM.setBaudRate(256000)self.open_status = Falseself.row_cnt = 0self.img = Noneself.timer = QtCore.QTimer()self.timer.timeout.connect(self.sendImage)self.startup()def startup(self):"""Write code here to run once"""for com_port in QtSerialPort.QSerialPortInfo.availablePorts():print(com_port.portName())# Try open serial portif not self.COM.open(QtSerialPort.QSerialPort.ReadWrite):self.open_status = Falseprint("Open Serial Port failed.")else:self.open_status = Truedef flip_lr(self):"""水平翻转回调函数"""if self.flip_horizontal == False:self.flip_horizontal = Trueself.btn3.setStyleSheet("QPushButton{color:rgb(128,128,255)}")else:self.flip_horizontal = Falseself.btn3.setStyleSheet("QPushButton{color:rgb(0,0,0)}")def flip_ud(self):"""垂直翻转回调函数"""if self.flip_vertical == False:self.flip_vertical = Trueself.btn4.setStyleSheet("QPushButton{color:rgb(128,128,255)}")else:self.flip_vertical = Falseself.btn4.setStyleSheet("QPushButton{color:rgb(0,0,0)}")def getfile(self):"""获取图像路径"""fname = QtWidgets.QFileDialog.getOpenFileName(self, 'Open file','C:\\Users\\Administrator\\Pictures', "Image files(*.jpg *.png)")self.clipImage(fname[0])self.updateImage()self.sendImage()def clipImage(self, fname):"""读取并裁剪图片至512x384大小"""if fname:img = cv2.imread(fname, cv2.IMREAD_COLOR)img_roi = img[:384,:512,:]print(img_roi.shape)cv2.imwrite('./img_roi.png', img_roi)def updateImage(self):"""显示裁剪后的图像"""self.img_widget.setPixmap(QtGui.QPixmap('./img_roi.png'))self.img = cv2.imread('./img_roi.png')if self.open_status:self.timer.start(100)def sendImage(self):"""通过串口发送图片"""pattern = ">2BH{:d}B".format(512*3)# 获取图像翻转信息flip_flag = 0x00if self.flip_horizontal:flip_flag = flip_flag + 0x10if self.flip_vertical:flip_flag = flip_flag + 0x01# 发送图像数据if self.open_status:if self.row_cnt == 384+3:self.row_cnt = 0self.timer.stop()else:args1 = [0x55, flip_flag, self.row_cnt]args2 = [rgb for rgb in self.img[(self.row_cnt % 384),:].reshape(-1)]send_data = struct.pack(pattern, *(args1+args2))self.row_cnt += 1self.COM.write(send_data)def closeEvent(self, event):super().closeEvent(event)#self.slider_window.close()# 定时器停止self.timer.stop()if self.open_status:self.COM.close() # 关闭串口def main():app = QtWidgets.QApplication(sys.argv)window = mainWindow('COM21')window.show()#for win in (window, window.slider_window):#   win.show()sys.exit(app.exec_())if __name__ == "__main__":main()