FPGA 实现任意角度图像旋转原理与代码设计

4. 第二级流水

计算图像旋转公式，以中心点为起始坐标 (0,0)，组合公式并右移 14 位。

reg signed [12:0] x_cos;
reg signed [12:0] y_sin;
reg signed [12:0] y_cos;
reg signed [12:0] x_sin;
assign row_abs = row_size;
assign col_abs = col_size;
assign row1 = row_abs >> 1;
assign col1 = col_abs >> 1;

always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) x_cos <= 'd0;
    else if(r_rotate_valid_1d) x_cos <= ((hcnt - col1) * cosout) >>> 14;
    else x_cos <= x_cos;
end
always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) y_sin <= 'd0;
    else if(r_rotate_valid_1d) y_sin <= ((vcnt - row1) * sinout) >>> 14;
    else y_sin <= y_sin;
end
always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) y_cos <= 'd0;
    else if(r_rotate_valid_1d) y_cos <= ((vcnt - row1) * cosout) >>> 14;
    else y_cos <= y_cos;
end
always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) x_sin <= 'd0;
    else if(r_rotate_valid_1d) x_sin <= ((hcnt - col1) * sinout) >>> 14;
    else x_sin <= x_sin;
end

5. 第三级流水

按照公式排列组合得出旋转后图像映射到原始图像的坐标位置。流程：原始屏幕坐标 -> 中心坐标系 -> 应用旋转公式 -> 旋转后的中心坐标 -> 转换回屏幕坐标系。

always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) r_rotate_valid_2d <= 'd0;
    else r_rotate_valid_2d <= r_rotate_valid_1d;
end
always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) hcnt_rotate <= 'd0;
    else if(r_rotate_valid_2d == 1'b1) hcnt_rotate <= x_cos - y_sin + (COL >> 1);
    else hcnt_rotate <= 'd0;
end
always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) vcnt_rotate <= 'd0;
    else if(r_rotate_valid_2d == 1'b1) vcnt_rotate <= y_cos + x_sin + (ROW >> 1);
    else vcnt_rotate <= 'd0;
end

6. 第四级流水线

判断 hcnt_rotate 和 vcnt_rotate 是否在原图像范围内，结合 data_cnt 计数器限制读取像素总数防止溢出。使用 ROM IP 核存储图像数据，第五级流水用于对齐 ROM 读出延迟。

always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) r_rotate_valid_3d <= 'd0;
    else r_rotate_valid_3d <= r_rotate_valid_2d;
end
always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) begin
        rden <= 'd0;
        addra <= 'd0;
    end else if(r_rotate_valid_3d == 1'b1) begin
        if((hcnt_rotate >= 'd0) && (hcnt_rotate < COL) && (vcnt_rotate >= 'd0) && (vcnt_rotate < ROW) && data_cnt < ROW * COL) begin
            rden <= 1'b1;
            addra <= COL * vcnt_rotate + hcnt_rotate;
        end else begin
            rden <= 1'b0;
            addra <= 'd0;
        end
    end else begin
        rden <= 'd0;
        addra <= 'd0;
    end
end
always @(posedge clk_i, negedge rstn_i) begin
    if (!rstn_i) data_cnt <= 'd0;
    else if (data_cnt == ROW * COL - 1) data_cnt <= 'd0;
    else if (r_rotate_valid_3d && (hcnt_rotate >= 'd0) && (hcnt_rotate < COL) && (vcnt_rotate >= 'd0) && (vcnt_rotate < ROW)) data_cnt <= data_cnt + 'd1;
end
img_mem_gen img_mem_gen_inst (
    .address(addra),
    .clock(clk_i),
    .rden(rden),
    .q(rom_data)
);

仿真结果

支持 30°、-30°、228° 等任意角度逆时针或顺时针旋转，功能正常。

总结

该方案实现了任意角度图像旋转，时序逻辑清晰，适用于 LCD 显示场景。核心在于利用 Cordic 算法生成三角函数值，并通过多级流水线完成坐标映射与数据读取。