如何从jpg图像中获取RGB888（24位）和RGB565（16位）帧缓冲转储？

Question

I need to resize ( either upscale or downscale) my image in jpg/png format. I'm using Bilinear interpolation to resize. My code works fine with values I gave in an array. But to test the result with an image, I need RGB565 and RGB888 dump.

As my task is to just resize the image, I would appreciate if I can get a dump with width and height of the image or just an algorithm would also do.

I am working on C. Please help me.

Thanks

Answer 1

If all you're missing is a conversion from RGB888 to RGB565, then it's easy. Call this following function for each pixel:

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);
}

Apply the function to all pixels. Each one will shrink from 3 bytes to 2 bytes.

Answer 2

My solution to convert a png to raw RGB 565 format in Python (called png2fb.py):

#!/usr/bin/python

import sys
from PIL import Image

if len(sys.argv) == 3:
    # print "\nReading: " + sys.argv[1]
    out = open(sys.argv[2], "wb")
elif len(sys.argv) == 2:
    out = sys.stdout
else:
    print "Usage: png2fb.py infile [outfile]"
    sys.exit(1)

im = Image.open(sys.argv[1])

if im.mode == "RGB":
    pixelSize = 3
elif im.mode == "RGBA":
    pixelSize = 4
else:
    sys.exit('not supported pixel mode: "%s"' % (im.mode))

pixels = im.tostring()
pixels2 = ""
for i in range(0, len(pixels) - 1, pixelSize):
    pixels2 += chr(ord(pixels[i + 2]) >> 3 | (ord(pixels[i + 1]) << 3 & 0xe0))
    pixels2 += chr(ord(pixels[i]) & 0xf8 | (ord(pixels[i + 1]) >> 5 & 0x07))
out.write(pixels2)
out.close()