滤镜之浮雕Emboss

首先看效果图：

 

这个算法是一个像素和它周围像素的差值加上一个灰度常数产生浮雕效果的图像。一般是和它左上方像素的差值为浮雕，是一种凸的效果，和右下角像素的差为雕刻，是一种凸的效果。代码中通过cos角度控制梯度方向。

 

这个滤镜在ImageStone这个软件中有完整代码，现在改写如下：

#define PI 3.1415926535897932384626433832795
void EmbossRGB(unsigned char* pInput,unsigned char* pOutput,int width,int height,int nStride,int nAngle)
{
	int intensity;
	unsigned char* src = pInput;
	unsigned char* dst = pOutput;
	unsigned char* p;
	int i,j,x,y,t;
	int offset = nStride-width*3;

	float dr = PI/4;
	float Weights[3][3];	
	float r = nAngle*PI/180.0;

	float sum = 0;

	if(pInput == NULL || pOutput == NULL)
		return;

	if(width <= 0 || height <= 0)
		return;
	
	Weights[0][0] = cos(r + dr) ;
	Weights[0][1] = cos(r + 2.0*dr) ;
	Weights[0][2] = cos(r + 3.0*dr) ;

	Weights[1][0] = cos(r) ;
	Weights[1][1] = 0 ;
	Weights[1][2] = cos(r + 4.0*dr) ;

	Weights[2][0] = cos(r - dr) ;
	Weights[2][1] = cos(r - 2.0*dr) ;
	Weights[2][2] = cos(r - 3.0*dr) ;

	// for each line
	for ( y = 0; y < height; y++ )
	{
		// for each pixel
		for ( x = 0; x < width; x++, src += 3, dst += 3 )
		{

			sum = 0;
			// for each kernel row
			for ( i = -1; i <= 1; i++ )
			{
				t = y + i;
				// skip row
				if ( t < 0 )
					continue;
				// break
				if ( t >= height )
					break;

				// for each kernel column
				for ( j = -1; j <= 1; j++ )
				{
					t = x + j;
					// skip column
					if ( t < 0 )
						continue;

					if ( t < width )
					{
						p = &src[i * nStride + j * 3];
						intensity = (int)( 0.2125 * (*p) + 0.7154 * (*(p+1))) + 0.0721 * (*(p+2));

						sum += intensity*Weights[i+1][j+1];
					}
				}
			}

			sum += 128;
			if(sum < 0)
				sum = 0;
			if(sum > 255)
				sum = 255;

			*dst = (unsigned char)sum;
			*(dst+1) = (unsigned char)(sum);
			*(dst+2) = (unsigned char)(sum);
		}
		src += offset;
		dst += offset;
	}
}