1 files changed, 89 insertions, 0 deletions
diff --git a/main.cpp b/main.cpp
new file mode 100755
index 0000000..bc7df66
--- /dev/null
+++ b/main.cpp
@@ -0,0 +1,89 @@
+#define STB_IMAGE_IMPLEMENTATION
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+#include "stb_image.h"
+#include "stb_image_write.h"
+
+#include <math.h>
+
+void doit(
+    const char *filenameIn,
+    const char *filenameOut,
+    stbi_uc r_fg_old,
+    stbi_uc g_fg_old,
+    stbi_uc b_fg_old,
+    stbi_uc r_bg,
+    stbi_uc g_bg,
+    stbi_uc b_bg,
+    stbi_uc r_fg_new,
+    stbi_uc g_fg_new,
+    stbi_uc b_fg_new)
+{
+    stbi_uc rDiff = abs(r_bg - r_fg_old);
+    stbi_uc gDiff = abs(g_bg - g_fg_old);
+    stbi_uc bDiff = abs(b_bg - b_fg_old);
+
+    int x, y, n;
+    stbi_uc *img = stbi_load(filenameIn, &x, &y, &n, 0);
+
+    for (int i = 0; i < x; i++) {
+        for (int j = 0; j < y; j++) {
+            size_t index = (j*x + i) * n;
+            stbi_uc r = img[index + 0];
+            stbi_uc g = img[index + 1];
+            stbi_uc b = img[index + 2];
+            stbi_uc a = img[index + 3];
+
+            stbi_uc rAbs = abs(r - r_fg_old);
+            double rNorm = (double)rAbs / rDiff;
+            stbi_uc gAbs = abs(g - g_fg_old);
+            double gNorm = (double)gAbs / gDiff;
+            stbi_uc bAbs = abs(b - b_fg_old);
+            double bNorm = (double)bAbs / bDiff;
+            
+            img[index + 0] = r_fg_new;
+            img[index + 1] = g_fg_new;
+            img[index + 2] = b_fg_new;
+            img[index + 3] =
+                (stbi_uc)(255.0*(1.0 - ((rNorm + gNorm + bNorm) / 3.0)));
+        }
+    }
+
+    stbi_write_png(filenameOut, x, y, n, img, 0);
+
+    stbi_image_free(img);
+}
+
+stbi_uc hex(char *c) {
+    stbi_uc c0 = 0, c1 = 0;
+    if (c[0] >= '0' && c[0] <= '9') c0 = c[0] - '0';
+    else if (c[0] >= 'a' && c[0] <= 'f') c0 = c[0] - 'a' + 10;
+    if (c[1] >= '0' && c[1] <= '9') c1 = c[1] - '0';
+    else if (c[1] >= 'a' && c[1] <= 'f') c1 = c[1] - 'a' + 10;
+    return c0*16 + c1;
+}
+
+int main(int argc, char **argv) {
+    if (argc != 6) {
+        fprintf(stderr, "Usage: %s filename_old filename_new fgcolor bgcolor fgcolor_new\n", argv[0]);
+        return 1;
+    }
+
+    // rgb, foreground and background and new foreground
+    stbi_uc r_f = hex(&argv[3][0]);
+    stbi_uc g_f = hex(&argv[3][2]);
+    stbi_uc b_f = hex(&argv[3][4]);
+    stbi_uc r_b = hex(&argv[4][0]);
+    stbi_uc g_b = hex(&argv[4][2]);
+    stbi_uc b_b = hex(&argv[4][4]);
+    stbi_uc r_n = hex(&argv[5][0]);
+    stbi_uc g_n = hex(&argv[5][2]);
+    stbi_uc b_n = hex(&argv[5][4]);
+    
+    doit(
+        argv[1], argv[2],
+        r_f, g_f, b_f,
+        r_b, g_b, b_b,
+        r_n, g_n, b_n);
+
+    return 0;
+}