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使用NDK在C/C++中解码YUV到RGB

androidc++candroid-ndkyuv
3
我想将Android摄像头的视频流转换为位图以进行图像处理。
我有一些代码可以将YUV转换为RGB，它在原生Java中工作正常，但这个过程不够快以用于实时视频处理，因此我认为在应用滤镜之前，需要先将其在C或C++中进行转换。我已经设置并运行了NDK，所以我唯一不知道如何做的就是将以下代码移植到C或C++：
// decode Y, U, and V values on the YUV 420 buffer described as YCbCr_422_SP by Android 
// David Manpearl 081201 
public void decodeYUV(int[] out, byte[] fg, int width, int height)
        throws NullPointerException, IllegalArgumentException {
    int sz = width * height;
    if (out == null)
        throw new NullPointerException("buffer out is null");
    if (out.length < sz)
        throw new IllegalArgumentException("buffer out size " + out.length
                + " < minimum " + sz);
    if (fg == null)
        throw new NullPointerException("buffer 'fg' is null");
    if (fg.length < sz)
        throw new IllegalArgumentException("buffer fg size " + fg.length
                + " < minimum " + sz * 3 / 2);
    int i, j;
    int Y, Cr = 0, Cb = 0;
    for (j = 0; j < height; j++) {
        int pixPtr = j * width;
        final int jDiv2 = j >> 1;
        for (i = 0; i < width; i++) {
            Y = fg[pixPtr];
            if (Y < 0)
                Y += 255;
            if ((i & 0x1) != 1) {
                final int cOff = sz + jDiv2 * width + (i >> 1) * 2;
                Cb = fg[cOff];
                if (Cb < 0)
                    Cb += 127;
                else
                    Cb -= 128;
                Cr = fg[cOff + 1];
                if (Cr < 0)
                    Cr += 127;
                else
                    Cr -= 128;
            }
            int R = Y + Cr + (Cr >> 2) + (Cr >> 3) + (Cr >> 5);
            if (R < 0)
                R = 0;
            else if (R > 255)
                R = 255;
            int G = Y - (Cb >> 2) + (Cb >> 4) + (Cb >> 5) - (Cr >> 1)
                    + (Cr >> 3) + (Cr >> 4) + (Cr >> 5);
            if (G < 0)
                G = 0;
            else if (G > 255)
                G = 255;
            int B = Y + Cb + (Cb >> 1) + (Cb >> 2) + (Cb >> 6);
            if (B < 0)
                B = 0;
            else if (B > 255)
                B = 255;
            out[pixPtr++] = 0xff000000 + (B << 16) + (G << 8) + R;
        }
    }

}

...

decodeYUV(argb8888, data, camSize.width, camSize.height);
Bitmap bitmap = Bitmap.createBitmap(argb8888, camSize.width,
                    camSize.height, Config.ARGB_8888);

有人知道如何做到这一点吗？

非常感谢！

更新

我已经做到了这一步：

JNIEXPORT void JNICALL Java_com_twothreetwo_zoomplus_ZoomPlus_YUVtoRGB(JNIEnv * env, jobject obj, jintArray rgb, jbyteArray yuv420sp, jint width, jint height)
{
    int             sz;
    int             i;
    int             j;
    int             Y;
    int             Cr = 0;
    int             Cb = 0;
    int             pixPtr = 0;
    int             jDiv2 = 0;
    int             R = 0;
    int             G = 0;
    int             B = 0;
    int             cOff;

    sz = width * height;
     //if(out == null) throw new NullPointerException("buffer 'out' is null");
     //if(out.length < sz) throw new IllegalArgumentException("buffer 'out' size " + out.length + " < minimum " + sz);
     //if(fg == null) throw new NullPointerException("buffer 'fg' is null");
     //if(fg.length < sz) throw new IllegalArgumentException("buffer 'fg' size " + fg.length + " < minimum " + sz * 3/ 2);
     for(j = 0; j < height; j++) {
             pixPtr = j * width;
             jDiv2 = j >> 1;
             for(i = 0; i < width; i++) {
                     Y = yuv420sp[pixPtr]; if(Y < 0) Y += 255;
                     if((i & 0x1) != 1) {
                             cOff = sz + jDiv2 * width + (i >> 1) * 2;
                             Cb = yuv420sp[cOff];
                             if(Cb < 0) Cb += 127; else Cb -= 128;
                             Cr = yuv420sp[cOff + 1];
                             if(Cr < 0) Cr += 127; else Cr -= 128;
                     }
                     R = Y + Cr + (Cr >> 2) + (Cr >> 3) + (Cr >> 5);
                     if(R < 0) R = 0; else if(R > 255) R = 255;
                     G = Y - (Cb >> 2) + (Cb >> 4) + (Cb >> 5) - (Cr >> 1) + (Cr >> 3) + (Cr >> 4) + (Cr >> 5);
                     if(G < 0) G = 0; else if(G > 255) G = 255;
                     B = Y + Cb + (Cb >> 1) + (Cb >> 2) + (Cb >> 6);
                     if(B < 0) B = 0; else if(B > 255) B = 255;
                     rgb[pixPtr++] = 0xff000000 + (B << 16) + (G << 8) + R;
             }
     }

}

但是我遇到了以下 C 语言错误：
apps/zoomplusndk/jni/zoomplusndk.c:53: warning: dereferencing 'void *' pointer
apps/zoomplusndk/jni/zoomplusndk.c:53: error: void value not ignored as it ought to be
apps/zoomplusndk/jni/zoomplusndk.c:56: warning: dereferencing 'void *' pointer
apps/zoomplusndk/jni/zoomplusndk.c:56: error: void value not ignored as it ought to be
apps/zoomplusndk/jni/zoomplusndk.c:58: warning: dereferencing 'void *' pointer
apps/zoomplusndk/jni/zoomplusndk.c:58: error: void value not ignored as it ought to be
apps/zoomplusndk/jni/zoomplusndk.c:67: warning: dereferencing 'void *' pointer
apps/zoomplusndk/jni/zoomplusndk.c:67: error: invalid use of void expression

第53行是Y = yuv420sp[pixPtr]; 如果Y < 0，那么Y将加上255。

3个回答
8
这是您修改过的代码：

这是您修改过的代码：

#include <jni.h>
#include <android/log.h>

int* rgbData;
int rgbDataSize = 0;

JNIEXPORT void JNICALL Java_mk_g6_transparency_CameraPreview_YUVtoRBG(JNIEnv * env, jobject obj, jintArray rgb, jbyteArray yuv420sp, jint width, jint height)
{
    int             sz;
    int             i;
    int             j;
    int             Y;
    int             Cr = 0;
    int             Cb = 0;
    int             pixPtr = 0;
    int             jDiv2 = 0;
    int             R = 0;
    int             G = 0;
    int             B = 0;
    int             cOff;
    int w = width;
    int h = height;
    sz = w * h;

    jbyte* yuv = yuv420sp;
    if(rgbDataSize < sz) {
        int tmp[sz];
        rgbData = &tmp[0];
        rgbDataSize = sz;
        __android_log_write(ANDROID_LOG_INFO, "JNI", "alloc");
    }

    for(j = 0; j < h; j++) {
             pixPtr = j * w;
             jDiv2 = j >> 1;
             for(i = 0; i < w; i++) {
                     Y = yuv[pixPtr];
                     if(Y < 0) Y += 255;
                     if((i & 0x1) != 1) {
                             cOff = sz + jDiv2 * w + (i >> 1) * 2;
                             Cb = yuv[cOff];
                             if(Cb < 0) Cb += 127; else Cb -= 128;
                             Cr = yuv[cOff + 1];
                             if(Cr < 0) Cr += 127; else Cr -= 128;
                     }
                     R = Y + Cr + (Cr >> 2) + (Cr >> 3) + (Cr >> 5);
                     if(R < 0) R = 0; else if(R > 255) R = 255;
                     G = Y - (Cb >> 2) + (Cb >> 4) + (Cb >> 5) - (Cr >> 1) + (Cr >> 3) + (Cr >> 4) + (Cr >> 5);
                     if(G < 0) G = 0; else if(G > 255) G = 255;
                     B = Y + Cb + (Cb >> 1) + (Cb >> 2) + (Cb >> 6);
                     if(B < 0) B = 0; else if(B > 255) B = 255;
                     rgbData[pixPtr++] = 0xff000000 + (B << 16) + (G << 8) + R;
             }
    }
    (*env)->SetIntArrayRegion(env, rgb, 0, sz, ( jint * ) &rgbData[0] );
}

这个还可以在线查看，网址是http://dl.dropbox.com/u/49855874/yuv-decoder.c

我的测试结果:

  • 在HTC Desire上，相机预览分辨率为640x480时处理时间约为20毫秒
  • 在HTC Desire上，相机预览分辨率为320x240时处理时间约为6毫秒
相机预览分辨率为640x480，处理速度为约20毫秒 - 在保持相同分辨率的情况下能否更好？... - Yuriy Chernyshov
2

在我修改了这一行之后，不再出现致命信号11(SIGSEGV)的错误:

jbyte* yuv = yuv420sp;

转换为：

jboolean isCopy;
jbyte* yuv = (*env)->GetByteArrayElements(env, yuv420sp, &isCopy);
1
我建议的是不要自己去做，因为已经有人完成得很完美了，可以使用GPUImage库或者移动这部分代码。
GPUImage也有一个Android版本： https://github.com/CyberAgent/android-gpuimage 如果你使用gradle，可以包含这个库并调用方法： GPUImageNativeLibrary.YUVtoRBGA(inputArray, WIDTH, HEIGHT, outputArray)。
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