Question

我在JPEG图片上执行隐写。我使用DCT系数来隐藏数据。我执行以下步骤：

将输入图像读入BufferedImage
从BufferedImage
应用前向DCT以获得DCT系数
在DCT系数中嵌入消息位
应用反DCT并将块写回BufferedImage

重复步骤2-5，直到没有剩余消息位，此时我将BufferedImage写入名为output.jpg的JPEG文件。值得一提的是，我不对整个图像应用DCT，而只对我嵌入消息位的块应用ouput.jpg。我正在使用this来源进行DCT，使用this来进行隐写术

问题：我最终得到static int[][] DCT_coefficients = new int[8][8]; static double[][] DCT_matrix = new double[8][8]; static int[][] Dequantized_m = new int[8][8]; static int[][] YBlock = new int[8][8]; static double[][] resultant = new double[8][8]; static int[][] red = new int[8][8]; static int[][] green = new int[8][8]; static int[][] blue = new int[8][8]; static int[][] Y = new int[8][8]; static int[][] Cb = new int[8][8]; static int[][] Cr = new int[8][8]; static int x = 0, y = 0; public static void main(String args[]) { //I retrieve a pixel block from **BufferedImage** and convert it to YCbCr double temp1, temp2, temp3, temp4; for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { Color c = new Color(input_image.getRGB(y, x)); red = c.getRed(); green = c.getGreen(); blue = c.getBlue(); YCbCr = YCrCb_conversion(red, green, blue); YBlock[i][j] = YCbCr[0]; Cb[i][j] = YCbCr[1]; Cr[i][j] = YCbCr[2]; y++; } x++; } //calculating DCT matrix for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { if (i == 0) { DCT_matrix[i][j] = 1 / Math.sqrt(8.0); } if (i > 0) { temp1 = 0.5; Apfloat Atemp1 = new Apfloat(temp1, 15); temp3 = ((2 * j) + 1) * i * java.lang.Math.PI; temp2 = temp3 / 16; Apfloat Atemp2 = new Apfloat(temp2, 15); temp4 = Math.cos(java.lang.Math.toRadians(temp2)); Apfloat Atemp4 = ApfloatMath.cos(Atemp2); Apfloat Atemp = Atemp4.multiply(Atemp1); DCT_matrix[i][j] = Atemp.doubleValue(); } } } //Leveling off Yblock for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { leveledoff[i][j] = pixel_block[i][j] - 128; } } // multiplying DCT matrix and leveled off YBlock resultant = matrix_multiply(DCT_matrix, leveledoff); // taking transpose of DCT matrix transpose = obj.transpose(DCT_matrix); //multiplying transpose with resultant to get DCT coefficient block DCT_Coefficients = matrix_multiply(resultant, trans); //quantizing DCT coefficients using 50 % quantization matrix for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { quantized_matrix[i][j] = (int) Math.round(DCT_Coefficients[i][j] / quantzation_matrix[i][j]); } } //Applying zigzag encoding ZigZag_encoded = zigzag.ZigzagEncode(quantised_m); //Encode data ZigZag_encoded = embed_data(ZigZag_encoded, data_buffer); //start IDCT IDCT(ZigZag_Encoded); //end main } //Method definitions //Method to change LSB of integer value public static int changeBit(int pixel, char bit) { String s = Integer.toBinaryString(pixel); char[] c = s.toCharArray(); c[c.length - 1] = bit; // converting binary to integer String n = ""; for (int y = 0; y < c.length; y++) { n += "" + c[y]; } int j = 0; for (int i = 0; i < n.length(); i++) { if (n.charAt(i) == '1') { j = j + pow(2, n.length() - 1 - i); } } return j; } // method to embed data public static int[] embed_data(int encoded[], char buffer[]) { for (int i = 0; i < buffer.length; i++) { int newVal = changeBit(encoded[i], buffer[i]); encoded[i] = newVal; } return encoded; } // Method to perform IDCT public static void IDCT(ZigZag_encoded) { //converting 1D zigzag array to 2D array quantised_matrix = Zigzag_Decode(ZigZag_encoded); //Dequantizing for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { Dequantized[i][j] = quantised_matrix[i][j] * quantzation_matrix[i][j]; } } // multiplying transpose of DCT matrix with Dequantized matrix resultant = matrix_multiply(transpose, Dequantized); //multiplying resultant with DCT matrix resultant = matrix_multiply(resultant, dct_mat); //adding 128 to each resultant entry and rounding off for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { block[i][j] = (int) Math.round(resultant[i][j] + 128); } } //Converting Yblock to RGB block YCrCbToRGB(block, Cb, Cr); //writing RGB block to BufferedImage for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { newcolor = new Color(red[i][j], green[i][j], blue[i][j]); input_image.setRGB(y, x, newcolor.getRGB()); y++; } x++; } } //method to convert RGB block to YCbCr public int[] YCrCb_conversion(int red, int green, int blue) { int[] YCbCr = new int[3]; //Y = 0.257R+ 0.504G + 0.098B + 16 YCbCr[0] = (int)(0.257 * red + 0.504 * green + 0.098 * blue) + 16; //Cb=–0.148R – 0.291G+ 0.439B + 128 YCbCr[1] = (int)((-0.148 * red - 0.291 * green + 0.439 * blue) + 128); //Cr = 0.439R – 0.368G – 0.071B + 128 YCbCr[2] = (int)((0.539 * red - 0.368 * green - 0.071 * blue) + 128); return value // index 0 holds values of Y 1 holds Cb values and 2 holds Cr vlaues return YCbCr; } //Method to convert YCbCr block to RGB block public static void YCrCbToRGB(int y[][], int Cb[][], int Cr[][]) { for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { //R = 1.164(Y – 16) + 1.596(Cr – 128) red[i][j] = (int)(1.164 * (y[i][j] - 16) + (1.596 * (Cr[i][j] - 128))); //G = 1.164(Y – 16) – 0.813(Cr – 128) – 0.391(Cb – 128) green[i][j] = (int)(1.164 * (y[i][j] - 16) - (0.813 * (Cr[i][j] - 128)) - (0.391 * (Cb[i][j] - 128))); //B = 1.164(Y – 16) + 2.018(Cb – 128) blue[i][j] = (int)(1.164 * (y[i][j] - 16) + (2.018 * (Cb[i][j] - 128))); } } }上的随机行，表示像素数据发生了显着变化。以下是图像写入代码：

 pixel block in Y space as input to DCT
 223  224  226  227  229  229  230  230 
 226  227  227  227  228  229  229  230 
 228  228  228  228  228  229  230  231 
 228  228  228  228  229  231  233  234 
 227  228  229  230  231  233  234  234 
 226  227  229  230  232  233  233  233 
 227  228  230  232  232  231  229  228 
 228  230  232  234  232  229  226  223

示例输入和输出：

 51  -1  0  0  0  0  0  0 
 -1  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0

量化后和嵌入数据之前的DCT系数矩阵：

50  -1  0  1  0  0  0  0 
 -1  0  1  0  0  0  0  0 
 1  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0 
 0  0  0  0  0  0  0  0

嵌入数据后的量化DCT系数：

 232  227  223  223  227  231  232  231 
 230  226  222  223  226  230  230  229 
 228  224  221  222  226  229  229  227 
 226  223  221  223  227  229  228  225 
 226  224  223  225  229  230  228  225 
 227  225  225  228  232  233  230  226 
 228  227  228  231  235  236  232  228 
 230  229  230  234  237  238  233  229

在嵌入数据并应用IDCT后，像素在Y空间中阻塞：

#huge_it_portfolio_content_1 #huge_it_portfolio_container_1 {
    max-width: 100%;
    width: 88% !important;
    opacity: 0;
    margin: auto;
}

input.jpg]

output.jpg]

我认为这是由于JPEG的有损性质所以我尝试了PNG但仍然遇到了同样的问题。

写入JPEG文件

0 个答案: