feat: support reading image from clipboard when no image_path is given

If <image_path> is omitted, reads image from clipboard using
wl-paste (Wayland) or xclip (X11), then passes the raw data to
mtmd_helper_bitmap_init_from_buf for decoding.

main.cpp

@@ -65,9 +65,40 @@ static std::string json_escape(const std::string & s) {
     return out;
 }
 
+static std::vector<unsigned char> read_clipboard() {
+    const char * cmd = nullptr;
+    if (getenv("WAYLAND_DISPLAY")) {
+        cmd = "wl-paste 2>/dev/null";
+    } else {
+        cmd = "xclip -selection clipboard -t image/png -o 2>/dev/null";
+    }
+    std::vector<unsigned char> data;
+    FILE * pipe = popen(cmd, "re");
+    if (!pipe) return data;
+    unsigned char buf[65536];
+    size_t n;
+    while ((n = fread(buf, 1, sizeof(buf), pipe)) > 0) {
+        data.insert(data.end(), buf, buf + n);
+    }
+    int st = pclose(pipe);
+    if (st != 0 || data.empty()) {
+        data.clear();
+        // fallback for X11: try without explicit target
+        if (!getenv("WAYLAND_DISPLAY")) {
+            pipe = popen("xclip -selection clipboard -o 2>/dev/null", "re");
+            if (pipe) {
+                while ((n = fread(buf, 1, sizeof(buf), pipe)) > 0)
+                    data.insert(data.end(), buf, buf + n);
+                pclose(pipe);
+            }
+        }
+    }
+    return data;
+}
+
 static void print_usage(const char * prog) {
     fprintf(stderr,
-        "Usage: %s -m <model> --mmproj <mmproj> [options] <image_path>\n"
+        "Usage: %s -m <model> --mmproj <mmproj> [options] [<image_path>]\n"
         "\n"
         "Options:\n"
         "  -m, --model  <path>    model file path (GGUF)\n"
@@ -81,9 +112,13 @@ static void print_usage(const char * prog) {
         "      --json              output in JSON format\n"
         "  -h                      show this help\n"
         "\n"
-        "Example:\n"
+        "If <image_path> is omitted, reads image from clipboard.\n"
-        "  %s -m model.gguf --mmproj mmproj.gguf -p \"OCR\" image.png\n",
+        "Requires wl-paste (Wayland) or xclip (X11) for clipboard support.\n"
-        prog, prog);
+        "\n"
+        "Examples:\n"
+        "  %s -m model.gguf --mmproj mmproj.gguf -p \"OCR\" image.png\n"
+        "  %s -m model.gguf --mmproj mmproj.gguf   # use clipboard image\n",
+        prog, prog, prog);
 }
 
 int main(int argc, char ** argv) {
@@ -134,17 +169,15 @@ int main(int argc, char ** argv) {
         }
     }
 
-    if ((optind + 1) != argc) {
-        print_usage(argv[0]);
-        return 1;
-    }
-    image_path = argv[optind];
-
     if (model_path.empty() || mmproj_path.empty()) {
         fprintf(stderr, "ERROR: -m/--model and --mmproj/--mm are required\n");
         return 1;
     }
 
+    if (optind < argc) {
+        image_path = argv[optind];
+    }
+
     signal(SIGINT, sigint_handler);
 
     int64_t t_start_us = ggml_time_us();
@@ -190,13 +223,35 @@ int main(int argc, char ** argv) {
 
     int64_t t_loaded_us = ggml_time_us();
 
-    mtmd_bitmap * bmp = mtmd_helper_bitmap_init_from_file(ctx_vision, image_path.c_str());
+    mtmd_bitmap * bmp = nullptr;
-    if (!bmp) {
+    if (!image_path.empty()) {
-        fprintf(stderr, "ERROR: failed to load image from %s\n", image_path.c_str());
+        bmp = mtmd_helper_bitmap_init_from_file(ctx_vision, image_path.c_str());
-        mtmd_free(ctx_vision);
+        if (!bmp) {
-        llama_free(lctx);
+            fprintf(stderr, "ERROR: failed to load image from %s\n", image_path.c_str());
-        llama_model_free(model);
+            mtmd_free(ctx_vision);
-        return 1;
+            llama_free(lctx);
+            llama_model_free(model);
+            return 1;
+        }
+    } else {
+        fprintf(stderr, "Reading image from clipboard...\n");
+        auto clip = read_clipboard();
+        if (clip.empty()) {
+            fprintf(stderr, "ERROR: clipboard is empty or no image found.\n"
+                            "Make sure wl-paste (Wayland) or xclip (X11) is installed.\n");
+            mtmd_free(ctx_vision);
+            llama_free(lctx);
+            llama_model_free(model);
+            return 1;
+        }
+        bmp = mtmd_helper_bitmap_init_from_buf(ctx_vision, clip.data(), clip.size());
+        if (!bmp) {
+            fprintf(stderr, "ERROR: failed to decode clipboard image.\n");
+            mtmd_free(ctx_vision);
+            llama_free(lctx);
+            llama_model_free(model);
+            return 1;
+        }
     }
 
     // Construct prompt using GLM-OCR chat template format