24位bmp到RGB565文件转换 [英] 24 bit bmp to RGB565 file conversion

问题描述

我想将24位bmp文件转换为RGB565格式以写入串行TFT彩色显示器.

I want to convert 24 bit bmp files to RGB565 format to write to a serial TFT colour display.

24位bmp的大小将始终为320x240像素，因为我的TFT显示屏为320x240

The size of the 24bit bmp will always be 320x240 pixels as my TFT display is 320x240

有人有这样做的经验吗?可能是C/C ++，Shell，Python，Java Script等...

Has anyone any experience of doing this? It could be C/C++, Shell, Python, Java Script and so on...

推荐答案

我将使用 NetPBM (体积更小，重量更轻)或 ImageMagick (体积更大的安装) )将BMP转换为易于解析的格式，然后使用 Perl 将其转换为RGB565格式.

I would use either NetPBM (much smaller and lighter-weight) or ImageMagick (much bigger installation) to convert the BMP into a format that is simple to parse and then use Perl to convert that to RGB565 format.

我假设您打算将RGB565数据写入帧缓冲区，所以您将执行以下操作:

I assume you are planning to write the RGB565 data to a frame buffer, so you would do something like:

./bmp2rgb565 image.bmp > /dev/fb1

因此，将以下内容另存为bmp2rgb565:

So, save the following as bmp2rgb565:

#!/bin/bash
################################################################################
# bmp2rgb565
# Mark Setchell
################################################################################

if [ $# -ne 1 ]; then 
   echo Usage: $0 image.bmp
   exit 1
fi

file=$1

# Use NetPBM's "bmptopnm" to convert BMP to PNM for easy reading
# You could use ImageMagick: convert "$file" PNM: | perl ...
bmptopnm "$file" 2> /dev/null | 
   perl -e '
      my $debug=0;   # Change to 1 for debugging

      # Discard first 3 lines of PNM header:
      #   P3
      #   320 240
      #   255
      my $line=<STDIN>; $line=<STDIN>; $line=<STDIN>;

      # Read file, 3 RGB bytes at a time
      {
         local $/ = \3;
         while(my $pixel=<STDIN>){
            # Extract 8-bit R,G and B from pixel
            my ($r,$g,$b)=unpack("CCC",$pixel);
            printf("R/G/B: %d/%d/%d\n",$r,$g,$b) if $debug;

            # Convert to RGB565
            my $r5=$r>>3;
            my $g6=$g>>2;
            my $b5=$b>>3;
            my $rgb565 = ($r5<<11) | ($g6<<5) | $b5;

            # Convert to little-endian 16-bit (VAX order) and write 2 bytes
            my $v=pack("v",$rgb565);
            syswrite(STDOUT,$v,2);
         }
      }
   '

我没有方便测试的帧缓冲区，但是应该很接近.

I don't have a frame buffer handy to test, but it should be pretty close.

请注意，您可以从以下代码开始使代码更健壮:

Note that you could make the code more robust by starting off with:

convert "$file" -depth 8 -resize 320x240\! PNM: | perl ...

这将确保图像始终与帧缓冲区大小匹配，并且它是8位而不是16位.如果BMP图像是上下颠倒还是从正面到背面，则可能还需要-flip或-flop.

which would make sure the image always matches the framebuffer size, and that it is 8-bit and not 16-bit. You may also want a -flip or -flop in there if the BMP image is upside-down or back-to-front.

请注意，如果使用 ImageMagick convert，该代码将适用于GIF，TIFF，JPEG，PNG和大约150种其他格式以及BMP.

Note that if you use ImageMagick convert, the code will work for GIFs, TIFFs, JPEGs, PNGs and around 150 other formats as well as BMP.

请注意，如果要测试代码，可以使用 ImageMagick 生成黑色图像，如下所示:

Note that if you want to test the code, you can generate a black image with ImageMagick like this:

convert -size 320x240 xc:black BMP3:black.bmp

，然后在运行时在输出中寻找一串零:

and then look for a bunch of zeroes in the output if you run:

./bmp2rgb565 black.bmp | xxd -g2

同样，您可以生成白色图像并查找一堆ff:

Likewise, you can generate a white image and look for a bunch of ffs:

convert -size 320x240 xc:red BMP3:white.bmp

以红色，绿色和蓝色依次类推:

And so on with red, green and blue:

convert -size 320x240 xc:red  BMP3:red.bmp
convert -size 320x240 xc:lime BMP3:green.bmp
convert -size 320x240 xc:blue BMP3:blue.bmp

# Or make a cyan-magenta gradient image
convert -size 320x240 gradient:cyan-magenta  cyan-magenta-gradient.bmp

示例:

./RGB565 red.bmp | xxd -g2 | more
00000000: 00f8 00f8 00f8 00f8 00f8 00f8 00f8 00f8  ................
00000010: 00f8 00f8 00f8 00f8 00f8 00f8 00f8 00f8  ................

示例:

./RGB565 blue.bmp | xxd -g2 | more
00000000: 1f00 1f00 1f00 1f00 1f00 1f00 1f00 1f00  ................
00000010: 1f00 1f00 1f00 1f00 1f00 1f00 1f00 1f00  ................

关键字::RGB565，rgb565，帧缓冲区，帧缓冲区，打包，解包，Perl，BMP，PGM，图像，Raspberry Pi，RASPI

Keywords: RGB565, rgb565, framebuffer, frame-buffer, pack, unpack, Perl, BMP, PGM, image, Raspberry Pi, RASPI

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