// 离散余弦变换核心
int DCT2D(double* cMatrix, double* pBmpMatrix, double* cMatrixT, int Nx, int Ny, int N, DCT2Mode mode, byte* insertData, int insertLen)
{
	// 如果在编码模式下
	if(mode == DCT2_ENCODE_MODE)
	{
		// 检测插入长度是否合法
		if
		(
		    (insertLen <= 0)          ||
		    (insertLen > Nx * Ny / 8) ||
		    (Nx == 0)                 ||
		    (Ny == 0)
		)
		{
			// 插入数据量过大，则退出
			fprintf(stdout, "You can't inserted bytes to the picture\n");
			exit(1);
		}
	}

	// 辅助数组
	double* pTmp = (double*)malloc(N * N * sizeof(double));
	int pBmpMatrixWith = Nx * N;

	// 插入索引位
	int insertIndex = 0;

	// 分块DCT变换
	for(int j = 0; j < Ny; j ++)
	{
		for(int i = 0; i < Nx; i ++)
		{
			int xOffset = i * N;
			int yOffset = j * N * pBmpMatrixWith;

			// 正交化乘以系数矩阵
			for(int dy = 0; dy < N; dy ++)
			{
				for(int dx = 0; dx < N; dx ++)
				{
					double sum = 0.0f;
					for(int sn = 0; sn < N; sn ++)
					{
						sum += (*(cMatrix + (dy * N + sn))) * (*(pBmpMatrix + (yOffset + sn * pBmpMatrixWith) + (xOffset+ dx)));
					}

					*(pTmp + (dy * N + dx)) = sum;
				}
			}

			// 正交化乘以转置系数矩阵
			for(int dy = 0; dy < N; dy ++)
			{
				for(int dx = 0; dx < N; dx ++)
				{
					double sum = 0.0f;
					for(int sn = 0; sn < N; sn ++)
					{
						sum += (*(pTmp + (dy * N + sn))) * (*(cMatrixT + (sn * N) + dx));
					}

					*(pBmpMatrix + (yOffset + dy * pBmpMatrixWith) + (xOffset+ dx)) = sum;
				}
			}

			// 逆变换模式
			if(mode == DCT2_INVERSE_TRANSFORM)
			{
				continue;
			}

			// 编码模式
			if(mode == DCT2_ENCODE_MODE)
			{
				double* pA = pBmpMatrix + (yOffset + 5 * pBmpMatrixWith) + (xOffset+ 5);
				double* pB = pBmpMatrix + (yOffset + 6 * pBmpMatrixWith) + (xOffset+ 6);

				// 采集密文bit位
				int insertV = ((int)(*(insertData + insertIndex / 8))) & ((int)(0x80 >> (insertIndex & 7)));

				if(insertV == 0)
				{
					if(*pA > *pB)
					{
						SWAP_DOUBLE(*pA, *pB);
					}

					*pB += 1.0f;
				}
				else
				{
					if(*pA < *pB)
					{
						SWAP_DOUBLE(*pA, *pB);
					}
					*pB -= 1.0f;
				}

				// 插入计数器
				insertIndex ++;
				continue;
			}

			// 解码模式
			if(mode == DCT2_DECODE_MODE)
			{
				double* pA = pBmpMatrix + (yOffset + 5 * pBmpMatrixWith) + (xOffset+ 5);
				double* pB = pBmpMatrix + (yOffset + 6 * pBmpMatrixWith) + (xOffset+ 6);
				byte* pInsertV = (byte*)(insertData + (insertIndex >> 3));

				if(*pA > *pB)
				{
					*pInsertV |= (byte)(0x80 >> (insertIndex & 7));
				}

				// 插入计数器
				insertIndex ++;
				continue;
			}
		}
	}

	// 释放辅助数组
	free(pTmp);
	return 0;
}
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