2020.4.27 xilinx PYNQ HLS开发 --以sobel为例

pynq的介绍：https://blog.csdn.net/xiaoqu001/article/details/79479208
pynq官方文档：http://pynq.readthedocs.io/en/latest/python_environment.html
pynq github开源项目：https://github.com/xilinx/pynq
pynq sobel github 代码：https://github.com/clancylea/pynq-sobel
使用hls编写sobel的硬件加速部分参考ug902，如有错误之处还请不吝赐教！
1.RGB转Y函数

unsigned char rgb2y(RGB pix)
{
#pragma HLS INLINE
  unsigned char y;
  y = ((66 * pix.R.to_int() + 129 * pix.G.to_int() + 25 * pix.B.to_int() + 128) >> 8) + 16;

  return y;
}

2.sobel 滤波操作函数
*注意这里edge_weight 可能会溢出，所以要加以判断。

RGB sobel_operator(WINDOW *window)
{
  short x_weight = 0;
  short y_weight = 0;

  short edge_weight;
  unsigned char edge_val;
  RGB pixel;

  char i;
  char j;


  const char x_op[3][3] = { {-1,0,1},
			    {-2,0,2},
			    {-1,0,1}};

  const char y_op[3][3] = { {1,2,1},
			    {0,0,0},
			    {-1,-2,-1}};

  //Compute approximation of the gradients in the X-Y direction
  for(i=0; i < 3; i++){
    for(j = 0; j < 3; j++){

      // X direction gradient
      x_weight = x_weight + (window->getval(i,j) * x_op[i][j]);

      // Y direction gradient
      y_weight = y_weight + (window->getval(i,j) * y_op[i][j]);
    }
  }

  edge_weight = ABS(x_weight) + ABS(y_weight);

  if(edge_weight > 255)
  {
//	printf("edge_weight = %d,uchar = %d\n",edge_weight,(unsigned char)edge_weight);
	edge_weight = 255;
  }

  edge_val = (255-(unsigned char)(edge_weight));

  //Edge thresholding
  if(edge_val > 200)
    edge_val = 255;
  else if(edge_val < 100)
    edge_val = 0;

  pixel.R = pixel.G = pixel.B = edge_val;

  return pixel;
}

3. load 像素到片上存储

void LoadPixelM2B(PIXEL *inter_pix,PIXEL input_buffer[MAX_WIDTH],int rows,int cols,int row,int row_l2p[1])
{
	static int in_offset;
	static int rows_c;
	static int cols_c;

	row_l2p[0] = row;

	if(row == 0)
	{
		in_offset = 0;
		rows_c = rows;
		cols_c = cols;
	}

	bool enable = row < rows_c;

	if(enable)
	{
		memcpy(input_buffer,(PIXEL *)(inter_pix + in_offset),cols_c*sizeof(PIXEL));
		in_offset += cols_c;
	}
}

4. 存储像素到DDR内存

void StorePixelB2M(PIXEL *out_pix,PIXEL output_buffer[MAX_WIDTH],int cols,int row_p2s[1])
{
	static int out_offset;
	static int cols_c;

	int row = row_p2s[0];
	if(row == 0){
		out_offset = 0;
		cols_c = cols;
	}
	bool enable = row > 0;
	if(enable)
	{
		memcpy((PIXEL *)(out_pix + out_offset),output_buffer,cols_c*sizeof(PIXEL));
		out_offset += cols_c;
	}
}

5.行缓冲和窗口缓冲处理过程

void Process(PIXEL input_buffer[MAX_WIDTH],PIXEL output_buffer[MAX_WIDTH],int rows,int cols,int row_l2p[1],int row_p2s[1])
{
	int col;
	int in_offset = 0;
	int out_offset = 0;

	Y_BUFFER buff_A;
	RGB_BUFFER buff_B;
	WINDOW buff_C;


	int row = row_l2p[0];
	for(col = 0; col < cols+1; col++){
#pragma HLS LOOP_TRIPCOUNT min=1920 max=1920
#pragma HLS DEPENDENCE variable=buff_A inter false
#pragma HLS PIPELINE II=1

		// Temp values are used to reduce the number of memory reads
		unsigned char temp;
//			RGB tempx;
		unsigned char tmpx_y;
		unsigned char test_val;

		//Line Buffer fill
		if(col < cols){
			buff_A.shift_up(col);
			temp = buff_A.getval(0,col);
		}

		//There is an offset to accomodate the active pixel region
		//There are only MAX_WIDTH and MAX_HEIGHT valid pixels in the image
		if(col < cols & row < rows){
			RGB new_pix;
			PIXEL input_pixel;
//				input_pixel = inter_pix[row][col];
			input_pixel = input_buffer[col];
			new_pix.B = input_pixel.range(7,0);
			new_pix.G = input_pixel.range(15,8);
			new_pix.R = input_pixel.range(23,16);
			tmpx_y = rgb2y(new_pix);
			buff_A.insert_bottom(tmpx_y,col);
		}

		//Shift the processing window to make room for the new column
		buff_C.shift_right();

		//The Sobel processing window only needs to store luminance values
		//rgb2y function computes the luminance from the color pixel
		if(col < cols){
			buff_C.insert(buff_A.getval(2,col),0,2);
			buff_C.insert(temp,1,2);
			buff_C.insert(tmpx_y,2,2);
		}
		RGB edge;

		//The sobel operator only works on the inner part of the image
		//This design assumes there are no edges on the boundary of the image
		if( row <= 1 || col <= 1 || row > (rows-1) || col > (cols-1)){
			edge.R = edge.G = edge.B = 0;
		}
		else{
		//Sobel operation on the inner portion of the image
			edge = sobel_operator(&buff_C);
		}

		//The output image is offset from the input to account for the line buffer
		if(row > 0 && col > 0){
			PIXEL output_pixel;
			ap_uint<8> padding = 0xff;
			output_pixel = (edge.R,edge.G);
			output_pixel = (output_pixel, edge.B);
			output_pixel = (padding,output_pixel);
//				out_pix[row-1][col-1] = output_pixel;
//				out_pix[(row-1)*cols + (col-1)] = output_pixel;
			output_buffer[col-1] = output_pixel;
		}
	}

	row_p2s[0] = row;
}

6. top 函数 使用Axi master接口和axilite接口，以及dataflow

void sobel_filter(PIXEL *inter_pix,PIXEL *out_pix, int rows, int cols)
{
#pragma HLS INTERFACE m_axi depth=2073600 port=inter_pix offset=slave bundle=DATA_IN
#pragma HLS INTERFACE m_axi depth=2073600 port=out_pix offset=slave bundle=DATA_OUT

#pragma HLS INTERFACE s_axilite register port=return bundle=CTRL_BUS
#pragma HLS INTERFACE s_axilite register port=inter_pix bundle=CTRL_BUS
#pragma HLS INTERFACE s_axilite register port=out_pix bundle=CTRL_BUS
#pragma HLS INTERFACE s_axilite register port=rows bundle=CTRL_BUS
#pragma HLS INTERFACE s_axilite register port=cols bundle=CTRL_BUS

	PIXEL input_buffer[MAX_WIDTH];
	PIXEL output_buffer[MAX_WIDTH];

	int row;
	int row_l2p[1];
	int row_p2s[1];
	for(row = 0; row < rows+1; row++){
#pragma HLS LOOP_TRIPCOUNT min=1080 max=1080
#pragma HLS DATAFLOW
		LoadPixelM2B(inter_pix, input_buffer, rows, cols, row, row_l2p);

		Process(input_buffer, output_buffer, rows, cols, row_l2p, row_p2s);

		StorePixelB2M(out_pix, output_buffer, cols, row_p2s);
	}
}