Add speechbubble alpha option

commands/image-editing/speechbubble.js

@@ -1,12 +1,25 @@
 import ImageCommand from "../../classes/imageCommand.js";
 
 class SpeechBubbleCommand extends ImageCommand {
-  params = {
+  params() {
-    water: "assets/images/speechbubble.png",
+    return {
+      water: this.specialArgs.alpha ? "assets/images/speech.png" : "assets/images/speechbubble.png",
       gravity: "north",
       resize: true,
       yscale: 0.2,
+      alpha: this.specialArgs.alpha
     };
+  }
+
+  static init() {
+    super.init();
+    this.flags.push({
+      name: "alpha",
+      description: "Make the top of the speech bubble transparent",
+      type: 5
+    });
+    return this;
+  }
 
   static description = "Adds a speech bubble to an image";
   static aliases = ["speech", "sb"];

natives/watermark.cc

@@ -22,6 +22,8 @@ Napi::Value Watermark(const Napi::CallbackInfo &info) {
     bool append = obj.Has("append")
                       ? obj.Get("append").As<Napi::Boolean>().Value()
                       : false;
+    bool alpha =
+        obj.Has("alpha") ? obj.Get("alpha").As<Napi::Boolean>().Value() : false;
     bool mc = obj.Has("mc") ? obj.Get("mc").As<Napi::Boolean>().Value() : false;
     string basePath = obj.Get("basePath").As<Napi::String>().Utf8Value();
     string type = obj.Get("type").As<Napi::String>().Utf8Value();
@@ -55,28 +57,6 @@ Napi::Value Watermark(const Napi::CallbackInfo &info) {
           watermark.resize((double)page_height / (double)watermark.height());
     }
 
-    vector<VImage> img;
-    int addedHeight = 0;
-    for (int i = 0; i < n_pages; i++) {
-      VImage img_frame =
-          type == "gif" ? in.crop(0, i * page_height, width, page_height) : in;
-      if (append) {
-        VImage appended = img_frame.join(watermark, VIPS_DIRECTION_VERTICAL,
-                                         VImage::option()->set("expand", true));
-        addedHeight = watermark.height();
-        img.push_back(appended);
-      } else if (mc) {
-        VImage padded =
-            img_frame.embed(0, 0, width, page_height + 15,
-                            VImage::option()->set("background", 0xffffff));
-        VImage composited =
-            padded.composite2(watermark, VIPS_BLEND_MODE_OVER,
-                              VImage::option()
-                                  ->set("x", width - 190)
-                                  ->set("y", padded.height() - 22));
-        addedHeight = 15;
-        img.push_back(composited);
-      } else {
     int x = 0, y = 0;
     switch (gravity) {
       case 1:
@@ -104,9 +84,62 @@ Napi::Value Watermark(const Napi::CallbackInfo &info) {
         y = page_height - watermark.height();
         break;
     }
+
+    vector<VImage> img;
+    int addedHeight = 0;
+    VImage contentAlpha;
+    VImage frameAlpha;
+    VImage bg;
+    VImage frame;
+    for (int i = 0; i < n_pages; i++) {
+      VImage img_frame =
+          type == "gif" ? in.crop(0, i * page_height, width, page_height) : in;
+      if (append) {
+        VImage appended = img_frame.join(watermark, VIPS_DIRECTION_VERTICAL,
+                                         VImage::option()->set("expand", true));
+        addedHeight = watermark.height();
+        img.push_back(appended);
+      } else if (mc) {
+        VImage padded =
+            img_frame.embed(0, 0, width, page_height + 15,
+                            VImage::option()->set("background", 0xffffff));
         VImage composited =
+            padded.composite2(watermark, VIPS_BLEND_MODE_OVER,
+                              VImage::option()
+                                  ->set("x", width - 190)
+                                  ->set("y", padded.height() - 22));
+        addedHeight = 15;
+        img.push_back(composited);
+      } else {
+        VImage composited;
+        if (alpha) {
+          if (i == 0) {
+            contentAlpha = watermark.extract_band(0).embed(
+                x, y, width, page_height,
+                VImage::option()->set("extend", "white"));
+            frameAlpha = watermark.extract_band(1).embed(
+                x, y, width, page_height,
+                VImage::option()->set("extend", "black"));
+            bg =
+                frameAlpha.new_from_image({0, 0, 0}).copy(VImage::option()->set(
+                    "interpretation", VIPS_INTERPRETATION_sRGB));
+            frame = bg.bandjoin(frameAlpha);
+            if (type == "jpg" || type == "jpeg") {
+              type = "png";
+            }
+          }
+          VImage content =
+              img_frame.extract_band(0, VImage::option()->set("n", 3))
+                  .bandjoin(contentAlpha & img_frame.extract_band(3));
+
+          composited =
+              content.composite2(frame, VIPS_BLEND_MODE_OVER,
+                                 VImage::option()->set("x", x)->set("y", y));
+        } else {
+          composited =
               img_frame.composite2(watermark, VIPS_BLEND_MODE_OVER,
                                    VImage::option()->set("x", x)->set("y", y));
+        }
         img.push_back(composited);
       }
     }