图像处理---LoMo

所谓Lomo效果无非就是四角变暗，然后加上颜色矩阵变换。

以下是通过c代码实现的Lomo效果，效果有待优化：

/** LOMO效果
 */
jintArray ToLOMO(JNIEnv *env, jobject obj, jintArray srcPixels, jint width,
        jint height, jfloat factor)
{

    jint* pixels = NULL;

    pixels = env->GetIntArrayElements(srcPixels, JNI_FALSE);
    if (pixels == NULL)
    {
        return srcPixels;
    }

    int size = width * height;
    int result[size];

    int ratio =
            width > height ? height * 32768 / width : width * 32768 / height;
    int cx = width >> 1;
    int cy = height >> 1;
    int max = cx * cx + cy * cy;
    int min = (int) (max * (1 - 0.8f));
    int diff = max - min;

    for (int i = 0; i < height; i++)
    {

        for (int j = 0; j < width; j++)
        {
            int current_color = pixels[i * width + j];

            int r0 = red(current_color);
            int g0 = green(current_color);
            int b0 = blue(current_color);
            int a0 = alpha(current_color);

            int value = r0 < 128 ? r0 : 256 - r0;
            int newR = (value * value * value) / 64 / 256;
            newR = r0 < 128 ? newR : 255 - newR;

            value = g0 < 128 ? g0 : 256 - g0;
            int newG = (value * value) / 128;
            newG = (g0 < 128 ? newG : 255 - newG);

            int newB = b0 / 2 + 0x25;

            /*****************边缘黑暗**************/
            int dx = cx - j;
            int dy = cy - i;

            if (width > height)
            {
                dx = (dx * ratio) >> 15;
            } else
            {
                dy = (dy * ratio) >> 15;
            }

            int distSq = dx * dx + dy * dy;

            if (distSq > min)
            {
                int v = ((max - distSq) << 8) / diff;
                v *= v;

                int ri = (int) (newR * v) >> 16;
                int gi = (int) (newG * v) >> 16;
                int bi = (int) (newB * v) >> 16;

                newR = ri > 255 ? 255 : (ri < 0 ? 0 : ri);
                newG = gi > 255 ? 255 : (gi < 0 ? 0 : gi);
                newB = bi > 255 ? 255 : (bi < 0 ? 0 : bi);
            }
            /**********************边缘黑暗end*****************/
            current_color = ARGB(a0, newR, newG, newB);
            result[i * width + j] = current_color;
        }
    }

    jintArray resultArray = env->NewIntArray(size);
    env->SetIntArrayRegion(resultArray, 0, size, result);
    env->ReleaseIntArrayElements(srcPixels, pixels, 0);
    return resultArray;
}

以上仅供参考，但是效率不是很高，不过还有一种实现方式，就是利用图层混合处理算法，此算法等我总结出来释放demo