Carve one vertical seam at a time
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@ -19,11 +19,18 @@ int min(int a, int b) {
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return a < b ? a : b;
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}
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/** e_1 energy */
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std::vector<unsigned char> energy_e1(unsigned char* source, int width, int height, int nbChannels) {
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std::vector<unsigned char> energy(width*height);
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void export_image(const char* filename, const void* data, int width, int height, int nbChannels) {
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if (!silent) std::cout << "Exporting to \"" << filename << "\".." << std::endl;
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int errcode = stbi_write_png(filename, width, height, nbChannels, data, nbChannels*width);
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if (!errcode) {
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std::cout<<"Error while exporting the resulting image."<<std::endl;
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exit(errcode);
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}
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}
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for (auto i=0; i < width*height; i++) { energy[i] = 0; }
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/** e_1 energy */
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std::vector<unsigned char> energy_e1(std::vector<unsigned char> source, int width, int height, int nbChannels) {
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std::vector<unsigned char> energy(width*height);
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for(auto i=0 ; i < width ; ++i) {
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for(auto j=0; j < height; ++j) {
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@ -33,6 +40,7 @@ std::vector<unsigned char> energy_e1(unsigned char* source, int width, int heigh
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auto indexPixel_left = (i-1 > 0) ? nbChannels*(width*j+(i-1)) : indexPixel;
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auto indexPixel_right = (i+1 < width) ? nbChannels*(width*j+(i+1)) : indexPixel;
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energy[width*j+i] = 0;
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for (auto ch=0; ch < nbChannels; ch++) {
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energy[width*j+i] += (
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fabs((float)source[indexPixel_up+ch] - source[indexPixel+ch])
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@ -47,7 +55,8 @@ std::vector<unsigned char> energy_e1(unsigned char* source, int width, int heigh
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return energy;
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}
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std::vector<int> optimal_vertical_seams(std::vector<unsigned char> energy, int width, int height, int nbSeams) {
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/** Given the energy value, returns the optimal vertical seam */
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std::vector<int> optimal_vertical_seam(std::vector<unsigned char> energy, int width, int height) {
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std::vector<unsigned char> dyn_energy(width*height);
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//* Find an end of the minimal connected vertical/horizontal seam
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@ -61,7 +70,6 @@ std::vector<int> optimal_vertical_seams(std::vector<unsigned char> energy, int w
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int bot_left = (i > 0 && j > 0) ? dyn_energy[width*(i-1)+(j-1)] : INT_MAX;
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int bot_right = (i > 0 && j+1 < width) ? dyn_energy[width*(i-1)+(j+1)] : INT_MAX;
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dyn_energy[width*i+j] = min(
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bot_center,
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min(
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@ -72,24 +80,19 @@ std::vector<int> optimal_vertical_seams(std::vector<unsigned char> energy, int w
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}
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}
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std::vector<int> result(height*nbSeams);
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// To find the nbSeams largest points, we sort the pairs (dyn_energy[idx, height-1], idx)
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std::vector<std::pair<int, int>> seamEnds(width);
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std::vector<int> result(height);
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// Find the seam end
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int min_idx = -1;
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int min_val = INT_MAX;
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for (auto j=0; j < width; j++) {
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seamEnds[j] = {dyn_energy[(height-1)*width+j], j};
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if (min_val > dyn_energy[width*(height-1)+j]) {
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min_idx = j;
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min_val = dyn_energy[width*(height-1)+j];
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}
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std::sort(seamEnds.begin(), seamEnds.end(),
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[](std::pair<int, int> a, std::pair<int, int> b) {return a.first > b.first; });
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for (auto seam=0; seam < nbSeams; seam++) {
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result[height*(seam+1)-1] = seamEnds[seam].second;
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}
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result[height-1] = min_idx;
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//* Backtracking to find the path
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for (auto seam=0; seam < nbSeams; seam++) {
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int min_idx = result[height*(seam+1)-1];
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int min_val = dyn_energy[(height-1)*width+min_idx];
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for (auto i=height-1; i > 0; i--) {
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// We want to find either (bot_l, bot_c, bot_r) with dyn_energy[.] = min_val - energy[cur]
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int objective_energy = min_val - energy[i*width+min_idx];
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@ -104,13 +107,40 @@ std::vector<int> optimal_vertical_seams(std::vector<unsigned char> energy, int w
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min_val = dyn_energy[(i-1)+height*(min_idx + 1)];
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min_idx = min_idx + 1;
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}
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result[height*seam+i-1] = min_idx;
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}
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result[i-1] = min_idx;
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}
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return result;
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}
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/** Carves an image by one vertical seam. Returns the optimal seam used */
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std::vector<int> carving_step_vertical(const std::vector<unsigned char> source, std::vector<unsigned char> &output, int width, int height, int nbChannels) {
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std::vector<unsigned char> energy = energy_e1(source, width, height, nbChannels);
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std::vector<int> opt_seam = optimal_vertical_seam(energy, width, height);
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std::vector<bool> blacklist(width*height);
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for (auto k=0; k < width*height; k++) { blacklist[k] = false; }
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for (auto i=0; i < height; i++) {
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blacklist[i*width+opt_seam[i]] = true;
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}
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int outWidth = width-1;
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for (auto i=0; i < height; i++) {
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int cur_j = 0;
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for (auto j=0; cur_j < outWidth && j < width; j++) {
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if (!blacklist[i*width+j]) {
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output[3*(i*(width-1)+cur_j)] = source[3*(i*width+j)];
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output[3*(i*(width-1)+cur_j)+1] = source[3*(i*width+j)+1];
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output[3*(i*(width-1)+cur_j)+2] = source[3*(i*width+j)+2];
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cur_j++;
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}
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}
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}
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return opt_seam;
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}
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int main(int argc, char **argv) {
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CLI::App app{"seam-carving"};
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@ -129,78 +159,70 @@ int main(int argc, char **argv) {
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//Image loading
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int width, height, nbChannels;
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unsigned char *source = stbi_load(sourceImage.c_str(), &width, &height, &nbChannels, 0);
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nbSeams = min(nbSeams, width);
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if (nbChannels < 3) { // TODO : really ?
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std::cout<< "Input images must be RGB images."<<std::endl;
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exit(1);
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}
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nbSeams = min(nbSeams, width);
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int outChannels = nbChannels;
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int outHeight = height;
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if (test_energy) { // Vertical seam carving. Prepare
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std::vector<unsigned char> output(width*height*3); // Final output (initial energy function + where we set removed pixels red)
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std::vector<unsigned char> carve_output(width*height*3); // Receives at each step the newly carved image
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std::vector<unsigned char> source_img(width*height*nbChannels); // Contains at each step the carved image
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std::vector<bool> complete_blacklist(width*height); // Contains all removed pixels
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for (auto k=0; k < width*height; k++) { complete_blacklist[k] = false; }
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for (auto i=0; i < width*height*nbChannels; i++) { source_img[i] = source[i]; }
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std::vector<unsigned char> ini_energy = energy_e1(source_img, width, height, nbChannels);
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//* Prepare final output
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for (auto k=0; k < width*height; k++) {
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//output[3*k] = source_img[3*k]/3; //* Uncomment if you prefer to see darkened source image
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//output[3*k+1] = source_img[3*k+1]/3;
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//output[3*k+2] = source_img[3*k+2]/3;
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output[3*k] = ini_energy[k];
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output[3*k+1] = ini_energy[k];
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output[3*k+2] = ini_energy[k];
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}
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int curWidth = width;
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for (auto seam=0; seam < nbSeams; seam++) {
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std::cout << seam << std::endl;
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std::vector<int> opt_seam = carving_step_vertical(source_img, carve_output, curWidth, height, nbChannels); // Perform a carving step
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std::copy(carve_output.begin(), carve_output.end(), source_img.begin()); // Copy output to next input
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curWidth--;
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for (auto i=0; i < height; i++) {
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int cur_j = 0; // cur_j is the index relative to the current carved image. j is absolute in the source image
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int j;
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for (j=0; j < width && cur_j < opt_seam[i]; j++) {
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if (!complete_blacklist[i*width+j]) { cur_j++; }
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}
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assert(cur_j == opt_seam[i]); // Else, j == width and cur_j is not in the source image..
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complete_blacklist[i*width+j] = true;
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output[3*(i*width+j)] = 255;
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}
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}
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export_image(outputImage.c_str(), output.data(), width, height, nbChannels);
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} else { // Standard vertical seam carving
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int outWidth = width;
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std::vector<unsigned char> output;
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std::vector<unsigned char> output(width*height*3);
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std::vector<unsigned char> vect_source(width*height*nbChannels);
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if (test_energy) {
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//outChannels = 1;
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std::vector<unsigned char> energy = energy_e1(source, width, height, nbChannels);
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std::vector<int> opt_seam = optimal_vertical_seams(energy, width, height, nbSeams);
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for (auto i=0; i < width*height*nbChannels; i++) { vect_source[i] = source[i]; }
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std::vector<unsigned char> output2(width*height*3);
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for (auto i=0; i < width*height; i++) {
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output2[3*i] = energy[i];
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output2[3*i+1] = energy[i];
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output2[3*i+2] = energy[i];
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}
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for (auto seam=0; seam < nbSeams; seam++) {
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for (auto i=0; i < height; i++) {
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output2[3*(i*width+opt_seam[seam*height+i])] = 255;
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output2[3*(i*width+opt_seam[seam*height+i])+1] = 0;
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output2[3*(i*width+opt_seam[seam*height+i])+2] = 0;
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std::cout << seam << std::endl;
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carving_step_vertical(vect_source, output, outWidth, height, nbChannels);
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std::copy(output.begin(), output.end(), vect_source.begin());
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outWidth--;
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}
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}
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output=output2;
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} else {
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std::vector<unsigned char> energy = energy_e1(source, width, height, nbChannels);
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std::vector<int> opt_seam = optimal_vertical_seams(energy, width, height, nbSeams);
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std::vector<bool> blacklist(width*height);
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for (auto k=0; k < width*height; k++) { blacklist[k] = false; }
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for (auto seam=0; seam < nbSeams; seam++) {
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bool overlap = false; // Check if 2 seams use similar pixels
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for (auto i=0; i < height; i++) {
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overlap = overlap || blacklist[i*width+opt_seam[seam*height+i]];
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}
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if (overlap) { nbSeams--; continue;}
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for (auto i=0; i < height; i++) {
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blacklist[i*width+opt_seam[seam*height+i]] = true;
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}
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}
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outWidth = width-nbSeams; //! something is weird here
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std::vector<unsigned char> output_l(outWidth*height*3);
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for (auto i=0; i < height; i++) {
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int cur_j = 0;
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for (auto j=0; cur_j < outWidth && j < width; j++) {
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if (!blacklist[i*width+j]) {
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output_l[3*(i*outWidth+cur_j)] = source[3*(i*width+j)];
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output_l[3*(i*outWidth+cur_j)+1] = source[3*(i*width+j)+1];
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output_l[3*(i*outWidth+cur_j)+2] = source[3*(i*width+j)+2];
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cur_j++;
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}
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}
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}
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output = output_l;
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}
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//Final export
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if (!silent) std::cout<<"Exporting.."<<std::endl;
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int errcode = stbi_write_png(outputImage.c_str(), outWidth, outHeight, outChannels, output.data(), outChannels*outWidth);
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if (!errcode) {
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std::cout<<"Error while exporting the resulting image."<<std::endl;
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exit(errcode);
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export_image(outputImage.c_str(), vect_source.data(), outWidth, height, nbChannels);
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}
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stbi_image_free(source);
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