From 4ee23bb4428927d13684017e393bb9f5d8351c1f Mon Sep 17 00:00:00 2001
From: augustin64 <me.git@augustin64.fr>
Date: Tue, 1 Apr 2025 18:27:35 +0200
Subject: [PATCH] Load mask

---
 src/seam-carving.cpp | 41 +++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/src/seam-carving.cpp b/src/seam-carving.cpp
index 0b22704..2a6a250 100644
--- a/src/seam-carving.cpp
+++ b/src/seam-carving.cpp
@@ -242,7 +242,7 @@ std::vector<int> carving_step(const std::vector<unsigned char> source_img,
 }
 
 void seam_carving(unsigned char *source, int width, int height, int nbChannels,
-                  const char *out_filename, int nbSeams, bool vertical) {
+                  const char *out_filename, int nbSeams, bool vertical, unsigned char* mask=nullptr) {
   int nbColorChannels = nbChannels > 3 ? 3 : nbChannels;
   int curWidth = width;
   int curHeight = height;
@@ -290,8 +290,8 @@ void seam_carving(unsigned char *source, int width, int height, int nbChannels,
       }
     }
     for (auto k = 0; k < width * height; k++) {
-      // for (auto i=0; i < nbColorChannels; i++) //* Uncomment if you prefer to
-      // see darkened source image
+      //* Uncomment if you prefer to see darkened source image
+      // for (auto i=0; i < nbColorChannels; i++)
       //   output[nbChannels*k+i] = source_img[nbChannels*k+i]/nbChannels;
 
       for (auto ch = 0; ch < nbColorChannels; ch++) {
@@ -347,8 +347,8 @@ void seam_carving(unsigned char *source, int width, int height, int nbChannels,
 
 int main(int argc, char **argv) {
   CLI::App app{"seam-carving"};
+  std::string maskImage;
   std::string sourceImage;
-  std::string maskImage = "mask.png";
   std::string outputImage = "output.png";
   int nbSeams = 1;
   bool vertical = false;
@@ -378,10 +378,39 @@ int main(int argc, char **argv) {
   int width, height, nbChannels;
   unsigned char *source =
       stbi_load(sourceImage.c_str(), &width, &height, &nbChannels, 0);
-  nbSeams = std::min(nbSeams, width);
+
+  unsigned char* mask = nullptr;
+  if (!maskImage.empty()) {
+    int maskWidth, maskHeight, maskChannels;
+    mask =
+      stbi_load(maskImage.c_str(), &maskWidth, &maskHeight, &maskChannels, 0);
+    
+      if (maskWidth != width || maskHeight != height) {
+        std::cerr << maskImage << " and " << sourceImage
+        << " differ in dimension. Please provide a valid mask."
+        << std::endl;
+        exit(1);
+      }
+      if (maskChannels < 3) {
+        std::cerr << maskImage << " needs to be RGB." << std::endl;
+        exit(1);
+      }
+      unsigned char r, g, b;
+      for (auto i=0; i < width*height; i++) {
+        r = mask[maskChannels*i];
+        g = mask[maskChannels*i];
+        b = mask[maskChannels*i];
+        mask[2*i]   = (r == 0) && (g == 255) && (b == 0);
+        mask[2*i+1] = (r == 255) && (g == 0) && (b == 0);
+      }
+      //* From now on, mask has the same dimensions as source and exactly 2 channels
+      //* The first channel is positive, the second one negative.
+  }
+
+  nbSeams = std::min(nbSeams, vertical ? width-1 : height-1); // We want to keep at least one row or column
 
   seam_carving(source, width, height, nbChannels, outputImage.c_str(),
-                nbSeams, vertical);
+                nbSeams, vertical, mask=mask);
 
   stbi_image_free(source);
   exit(0);