Android系统中Y'UV420p (NV21)到ARGB8888的转换

古城微笑少年丶 2021-11-10 03:18 240阅读 0赞

[http://en.wikipedia.org/wiki/YUV][http_en.wikipedia.org_wiki_YUV]

This format (NV21) is the standard picture format on android camera preview. YUV 4:2:0 planar image, with 8 bit Y samples, followed by interleaved V/U plane with 8bit 2x2 subsampled chroma samples.[\[8\]][8]

Java source code used on Android:

但是NV21在Microsoft中的定义是：

Microsoft defines this format as follows:

>  "The same as [NV12][], except that Cb and Cr samples are swapped so that the chroma array of unsigned char would have Cr followed by Cb for each sample (such that if addressed as a little-endian WORD type, Cr would be in the LSBs and Cb would be in the MSBs)."
> 
> 参考： [http://www.fourcc.org/yuv.php][http_www.fourcc.org_yuv.php]

/**
     * Converts YUV420 NV21 to ARGB8888
     * 
     * @param data byte array on YUV420 NV21 format.
     * @param width pixels width
     * @param height pixels height
     * @return a ARGB8888 pixels int array. Where each int is a pixels ARGB. 
     */
    public static int[] convertYUV420_NV21toARGB8888(byte [] data, int width, int height) {
        int size = width*height;
        int offset = size;
        int[] pixels = new int[size];
        int u, v, y1, y2, y3, y4;
     
        // i along Y and the final pixels
        // k along pixels U and V
        for(int i=0, k=0; i < size; i+=2, k+=2) {
            y1 = data[i  ]&0xff;
            y2 = data[i+1]&0xff;
            y3 = data[width+i  ]&0xff;
            y4 = data[width+i+1]&0xff;
     
            u = data[offset+k  ]&0xff;
            v = data[offset+k+1]&0xff;
            u = u-128;
            v = v-128;
     
            pixels[i  ] = convertYUVtoARGB(y1, u, v);
            pixels[i+1] = convertYUVtoARGB(y2, u, v);
            pixels[width+i  ] = convertYUVtoARGB(y3, u, v);
            pixels[width+i+1] = convertYUVtoARGB(y4, u, v);
     
            if (i!=0 && (i+2)%width==0)
                i+=width;
        }
     
        return pixels;
    }
     
    private static int convertYUVtoARGB(int y, int u, int v) {
        int r,g,b;
     
        r = y + (int)1.402f*u;
        g = y - (int)(0.344f*v +0.714f*u);
        b = y + (int)1.772f*v;
        r = r>255? 255 : r<0 ? 0 : r;
        g = g>255? 255 : g<0 ? 0 : g;
        b = b>255? 255 : b<0 ? 0 : b;
        return 0xff000000 | (r<<16) | (g<<8) | b;
    }

[http://stackoverflow.com/questions/16737749/onpreviewframe-yuv-grayscale-skewed][http_stackoverflow.com_questions_16737749_onpreviewframe-yuv-grayscale-skewed]

[http://stackoverflow.com/questions/8340128/decoding-yuv-to-rgb-in-c-c-with-ndk][http_stackoverflow.com_questions_8340128_decoding-yuv-to-rgb-in-c-c-with-ndk]

[http://msdn.microsoft.com/zh-cn/library/windowsphone/develop/microsoft.devices.photocamera.ycbcrpixellayout(v=vs.105).aspx][http_msdn.microsoft.com_zh-cn_library_windowsphone_develop_microsoft.devices.photocamera.ycbcrpixellayout_v_vs.105_.aspx]

在Android API Level-9中YUV格式采用YV12（YVU420）格式，而且若Y分量的宽度不是16的整倍数时，进行扩展。但是Y分量的高是奇数时，U，V分量的高是hight/2

[http://stackoverflow.com/questions/16737749/onpreviewframe-yuv-grayscale-skewed][http_stackoverflow.com_questions_16737749_onpreviewframe-yuv-grayscale-skewed]

> public static final int YV12
> 
> Added in API level 9 Android YUV format.
> 
> This format is exposed to software decoders and applications.
> 
> YV12 is a 4:2:0 YCrCb planar format comprised of a WxH Y plane followed by (W/2) x (H/2) Cr and Cb planes.
> 
> This format assumes
> 
> an even width an even height a horizontal stride multiple of 16 pixels a vertical stride equal to the height y\_size = stride \* height c\_stride = ALIGN(stride/2, 16) c\_size = c\_stride \* height/2 size = y\_size + c\_size \* 2 cr\_offset = y\_size cb\_offset = y\_size + c\_size

[http_en.wikipedia.org_wiki_YUV]: http://en.wikipedia.org/wiki/YUV
[8]: http://en.wikipedia.org/wiki/YUV#cite_note-8
[NV12]: http://www.fourcc.org/yuv.php#NV12
[http_www.fourcc.org_yuv.php]: http://www.fourcc.org/yuv.php
[http_stackoverflow.com_questions_16737749_onpreviewframe-yuv-grayscale-skewed]: http://stackoverflow.com/questions/16737749/onpreviewframe-yuv-grayscale-skewed
[http_stackoverflow.com_questions_8340128_decoding-yuv-to-rgb-in-c-c-with-ndk]: http://stackoverflow.com/questions/8340128/decoding-yuv-to-rgb-in-c-c-with-ndk
[http_msdn.microsoft.com_zh-cn_library_windowsphone_develop_microsoft.devices.photocamera.ycbcrpixellayout_v_vs.105_.aspx]: http://msdn.microsoft.com/zh-cn/library/windowsphone/develop/microsoft.devices.photocamera.ycbcrpixellayout%28v=vs.105%29.aspx