Fix Trim command when top-left corner is non-transparent (fix #1659)

src/app/doc_api.cpp

@@ -324,11 +324,59 @@ void DocApi::trimSprite(Sprite* sprite, const bool byGrid)
 
   for (frame_t frame(0); frame<sprite->totalFrames(); ++frame) {
     render.renderSprite(image, sprite, frame);
-
-    // TODO configurable (what color pixel to use as "refpixel",
-    // here we are using the top-left pixel by default)
     gfx::Rect frameBounds;
-    if (doc::algorithm::shrink_bounds(image, frameBounds, get_pixel(image, 0, 0)))
+
+    // Before this fix, we did use the top-left corner pixel by default as "refColor" in
+    // doc::algorithm::shrink_bounds(image, frameBounds, refColor).
+    // Now, we are looking for one color whole border (i.e: solid color border)
+    // searching on the sprite square contour.
+    //
+    // If the algorithm finds a transparentColor pixel on border frame,
+    // automatically "refColor" turns to transparentColor and it goes directly to
+    // shrink_bounds function.
+    // If the borders don't contain transparentColor, the algorithm keeps checking:
+    // It search for a solid color border (top border first), then it checks
+    // the opposite border (bottom border), then:
+    // 1- If the opposite border color is equal to the first border,
+    //    this color will be the "refColor".
+    // 2- If the color of the opposite border is solid, BUT different to the first
+    //    border we have to trigger a dialog, delegating the choise to the user.
+    // 3- If opposite border contains differents colors, we choose the first border color as
+    //    "refColor".
+    // 4- It repeat analisys to sprite left and right columns pixels.
+    // If no border has solid color, trimSprite do nothing.
+
+    bool skipTrim = false;
+    bool analizeMoreBorders = true;
+    color_t refColor = get_pixel(image, 0, 0);
+    bool firstBorderIsSolidColor = true;
+    bool secondBorderIsSolidColor = true;
+    const color_t probableRefColor1 = refColor;
+    const color_t probableRefColor2 = get_pixel(image, sprite->width() - 1, sprite->height() - 1);
+
+    if (analizeFrameSpritePixels(image, sprite, refColor,
+                                 firstBorderIsSolidColor,
+                                 secondBorderIsSolidColor, true)) {
+      // Here, we know that analizeFrameSpritePixels did not find transparent pixels on top and bottom borders.
+      if (!firstBorderIsSolidColor && secondBorderIsSolidColor)
+        refColor = probableRefColor2;
+      else if (firstBorderIsSolidColor && secondBorderIsSolidColor && probableRefColor1 != probableRefColor2) {
+        // Both border are solids colors but different, so we have to trigger the dialog
+        skipTrim = true;
+        analizeMoreBorders = false;
+      }
+      if (analizeMoreBorders && analizeFrameSpritePixels(image, sprite, refColor,
+                                                         firstBorderIsSolidColor,
+                                                         secondBorderIsSolidColor, false)) {
+        if (!firstBorderIsSolidColor && secondBorderIsSolidColor)
+          refColor = probableRefColor2;
+        else if (firstBorderIsSolidColor && secondBorderIsSolidColor && probableRefColor1 != probableRefColor2)
+          // Both border are solids colors but different, so we have to trigger the dialog
+          skipTrim = true;
+      }
+    }
+
+    if (!skipTrim && doc::algorithm::shrink_bounds(image, frameBounds, refColor))
       bounds = bounds.createUnion(frameBounds);
 
     // TODO merge this code with the code in DocExporter::captureSamples()
@@ -351,6 +399,61 @@ void DocApi::trimSprite(Sprite* sprite, const bool byGrid)
     cropSprite(sprite, bounds);
 }
 
+bool DocApi::analizeFrameSpritePixels(Image* image,
+                                      const Sprite* sprite,
+                                      color_t& refColor,
+                                      bool& firstBorderIsSolidColor,
+                                      bool& secondBorderIsSolidColor,
+                                      bool topBottomLookUp) {
+  firstBorderIsSolidColor = true;
+  secondBorderIsSolidColor = true;
+  int spriteW = sprite->width();
+  int spriteH = sprite->height();
+  const color_t probableRefColor1 = get_pixel(image, 0, 0);
+  const color_t probableRefColor2 = get_pixel(image, spriteW - 1, spriteH - 1);
+  if (!topBottomLookUp) {
+    int aux = spriteW;
+    spriteW = spriteH;
+    spriteH = aux;
+  }
+  color_t currentPixel = 0;
+  color_t transparentColor = sprite->transparentColor();
+
+  if (probableRefColor1 == transparentColor || probableRefColor2 == transparentColor) {
+    refColor = transparentColor;
+    return false;
+  }
+
+  for (int i=0; i < spriteW; i++) {
+    if (topBottomLookUp)
+      currentPixel = get_pixel(image, i, 0);
+    else
+      currentPixel = get_pixel(image, 0, i);
+    if (currentPixel != probableRefColor1) {
+      firstBorderIsSolidColor = false;
+      if (currentPixel == transparentColor) {
+        refColor = transparentColor;
+        return false;
+      }
+    }
+  }
+
+  for (int i=0; i < spriteW; i++) {
+    if (topBottomLookUp)
+      currentPixel = get_pixel(image, i, spriteH - 1);
+    else
+      currentPixel = get_pixel(image, spriteH - 1, i);
+    if (currentPixel != probableRefColor2) {
+      secondBorderIsSolidColor = false;
+      if (currentPixel == transparentColor) {
+        refColor = transparentColor;
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
 void DocApi::addFrame(Sprite* sprite, frame_t newFrame)
 {
   copyFrame(sprite, newFrame-1, newFrame,

src/app/doc_api.h

@@ -117,6 +117,12 @@ namespace app {
     void setPalette(Sprite* sprite, frame_t frame, const Palette* newPalette);
 
   private:
+    bool analizeFrameSpritePixels(Image* image,
+                                  const Sprite* sprite,
+                                  color_t& refColor,
+                                  bool& firstBorderIsSolidColor,
+                                  bool& secondBorderIsSolidColor,
+                                  bool topBottomLookUp);
     void cropImageLayer(LayerImage* layer,
                         const gfx::Rect& bounds,
                         const bool trimOutside);