rgb888 转 rgb565，并验证转换是否成功（python）

旧城等待， 2023-01-20 09:45 34阅读 0赞

在 k210 上做 AI 开发，遇到了一个显示图片的问题。（摄像头采集的图片有两种格式，自带rgb565，我用的不是摄像头，用的是图片数组验证模型推理结果，所以遇到了这个问题）

模型推理成功后，怎么才能在 LCD 上显示出来？

小学弟提醒说：LCD 显示的是 RGB565 格式的图片，而正常的图片保存格式是 RGB888，那么解决方法有两个：

1.  在项目工程中将图片转为 RGB565，（c 语言）
2.  在电脑中将图片转为 RGB565 （python 语言）

--------------------

unsigned short int rgb888Torgb565(unsigned int rgb888Pixel)
    {
        
        int red   = (rgb888Pixel >> 16) & 0xff;
        int green = (rgb888Pixel >> 8 ) & 0xff;
        int blue  =  rgb888Pixel        & 0xff;
    
        unsigned short  b =   (blue  >> 3) & 0x001f;
        unsigned short  g = ( (green >> 2) & 0x003f ) << 6;
        unsigned short  r = ( (red   >> 3) & 0x001f ) << 11;
    
        return (unsigned short int) (r | g | b);
    }

k210 版本

void rgb888_to_lcd(uint8_t *src, uint16_t *dest, size_t width, size_t height)
    {
        
        size_t i, chn_size = width * height;
        for (size_t i = 0; i < width * height; i++)
        {
        
            uint8_t r = src[i];
            uint8_t g = src[chn_size + i];
            uint8_t b = src[chn_size * 2 + i];
    
            uint16_t rgb = ((r & 0b11111000) << 8) | ((g & 0b11111100) << 3) | (b >> 3);
            size_t d_i = i % 2 ? (i - 1) : (i + 1);
            dest[d_i] = rgb;
        }
    }

--------------------

而我当然是选择后者了。人生苦短，我用python。

网上找了一圈，都是各种显示 rgb565 的 python 代码，并没有 rgb888 转 rgb565 的详细代码，还好我没放弃，在 github 中找到了这么一份代码，github 地址在参考目录中有。

源码其实很简单的，核心就是这么几行：

R = pix[w, h][0] >> 3
    G= pix[w, h][1] >> 2
    B = pix[w, h][2] >> 3
    
    rgb = (R << 11) | (G << 5) | B

# coding=utf-8
    '''
    @ Summary: img2rgb565() 函数将图片保存为 RGB565
               show_rgb565() 将rgb565反转为rgb888并显示图片
    @ Update:  
    
    @ file:    png2rgb565.py
    @ version: 1.0.0
    
    @ Author:  Lebhoryi@gmail.com
    @ Date:    2021/5/11 18:41
    @ Link:    https://github.com/jimmywong2003/PNG-to-RGB565/blob/master/png2rgb565.py
    
    @ Example:
                python png2rgb565.py NRF52840_DK_ILI9341.png NRF52840_DK.h NRF52840.bin
    '''
    import sys
    from PIL import Image
    import struct
    import cv2
    import numpy as np
    
    isSWAP = False
    
    def img2rgb565():
        len_argument = len(sys.argv)
        if (len_argument != 4):
            print("")
            print("Correct Usage:")
            print("\tpython png2rgb565.py <png_file> <include_file> <binary_file>")
            print("")
            sys.exit(0)
    
        try:
            im = Image.open(sys.argv[1])
        except:
            raise Exception(f"Fail to open png file {
          sys.argv[1]}")
    
        image_height = im.size[1]
        image_width = im.size[0]
    
        try:
            outfile = open(sys.argv[2], "w")
        except:
            raise Exception(f"Can't write the file {
          sys.argv[2]}")
    
    
        try:
            binoutfile = open(sys.argv[3], "wb")
        except:
            raise Exception(f"Can't write the binary file {
          im.size[3]}")
    
    
        print(f"/* Image Width:{
          im.size[0]} Height:{
          im.size[1]} */", file=outfile)
        print("const static uint16_t Hand_10[] = {", file=outfile)
    
        pix = im.load()  # load pixel array
        for h in range(image_height):
            for w in range(image_width):
                if ((h * 16 + w) % 16 == 0):
                    print(" ", file=outfile)
                    print("\t\t", file=outfile, end='')
    
                if w < im.size[0]:
                    R = pix[w, h][0] >> 3
                    G = pix[w, h][1] >> 2
                    B = pix[w, h][2] >> 3
    
                    rgb = (R << 11) | (G << 5) | B
    
                    if (isSWAP == True):
                        swap_string_low = rgb >> 8
                        swap_string_high = (rgb & 0x00FF) << 8
                        swap_string = swap_string_low | swap_string_high
                        print("0x%04x, " % (swap_string), file=outfile, end='')
                        binoutfile.write(struct.pack('H', swap_string))
                    else:
                        print("%04d, " % (rgb), file=outfile, end='')
                        binoutfile.write(struct.pack('H', rgb))
                else:
                    rgb = 0
    
        print("", file=outfile)
        print("};", file=outfile)
    
        outfile.close()
        binoutfile.close()
    
        print(f"Image file {
          sys.argv[1]} converted to {
          sys.argv[2]} done.")
        return sys.argv[2]
    
    
    def show_rgb565(img_file):
        # Read 16-bit RGB565 image into array of uint16
        with open(img_file, 'r') as f:
            lines = f.read().split()
        lines = lines[11:-1]
        lines = list(map(lambda i: int(i[:-1]), lines))
        image = np.array(lines)
        rgb565array = np.reshape(image, (224, 224))
    
    
        # Pick up image dimensions
        h, w = rgb565array.shape
    
        # Make a numpy array of matching shape, but allowing for 8-bit/channel for R, G and B
        rgb888array = np.zeros([h, w, 3], dtype=np.uint8)
    
        for row in range(h):
            for col in range(w):
                # Pick up rgb565 value and split into rgb888
                rgb565 = rgb565array[row, col]
                r = ((rgb565 >> 11) & 0x1f) << 3
                g = ((rgb565 >> 5) & 0x3f) << 2
                b = ((rgb565) & 0x1f) << 3
                # Populate result array
                rgb888array[row, col] = r, g, b
    
        # Save result as PNG
        # Image.fromarray(rgb888array).save('result.png')
        rgb888array = cv2.cvtColor(rgb888array, cv2.COLOR_RGB2BGR)
        cv2.imshow("result", rgb888array)
        cv2.waitKey(2000)
        cv2.destroyWindow("result")
    
    
    def main():
        img_file = img2rgb565()
        show_rgb565(img_file)
    
    if __name__ == "__main__":
        main()

参考：

*  show rgb565: https://www.thinbug.com/q/52027382
 *  https://github.com/jimmywong2003/PNG-to-RGB565