图片alpha处理与透明处理

src/Raster.cc

@@ -377,6 +377,42 @@ void Raster::drawImageWithKey(int startX, int startY, const Image* image, Rgba k
     }
 }
 
+void Raster::drawImageAlphaTest(int startX, int startY, const Image* image, byte alpha) {
+    /*越界部分不描画*/
+    int left = tmax<int>(startX, 0);
+    int bottom = tmax<int>(startY, 0);
+
+    int right = tmin<int>(startX + image->width(), _width);
+    int top = tmin<int>(startY + image->height(), _height);
+
+    for (int x = left; x < right; x++) {
+        for (int y = bottom; y < top; y++) {
+            Rgba color = image->pixelAt(x - left, y - bottom);
+            if (color._a > alpha) {
+                setPixel(x, y, color);
+            }
+        }
+    }
+}
+
+void Raster::drawImageAlphaBlend(int startX, int startY, const Image* image, float alpha) {
+    /*越界部分不描画*/
+    int left = tmax<int>(startX, 0);
+    int bottom = tmax<int>(startY, 0);
+
+    int right = tmin<int>(startX + image->width(), _width);
+    int top = tmin<int>(startY + image->height(), _height);
+
+    for (int x = left; x < right; x++) {
+        for (int y = bottom; y < top; y++) {
+            Rgba dstColor = image->pixelAt(x - left, y - bottom);
+            Rgba srcColor = getPixel(x, y);
+            Rgba color = colorLerp(srcColor, dstColor, dstColor._a / 255.0f * alpha);
+            setPixel(x, y, color);
+        }
+    }
+}
+
 int Raster::size() {
     return _width * _height * sizeof (Rgba);
 }
@@ -393,6 +429,10 @@ bool Raster::setPixel(int x, int y, Rgba color) {
     buffer[ ((_height - 1) - y) * _width + x] = color;
 }
 
+Rgba Raster::getPixel(int x, int y) {
+    return buffer[ ((_height - 1) - y) * _width + x];
+}
+
 bool Raster::isIn(int2 point) {
     if (point.x >= 0 && point.x <= _width && point.y >= 0 && point.y < _height) {
         return true;

src/Raster.h

@@ -97,9 +97,12 @@ public:
     void drawRect(const int2* points, const Rgba* colors);
     void drawImage(int startX, int startY, const Image* image);
     void drawImageWithKey(int startX, int startY, const Image* image, Rgba key);
+    void drawImageAlphaTest(int startX, int startY, const Image* image, byte key);
+    void drawImageAlphaBlend(int startX, int startY, const Image* image, float alpha = 1);
     int size();
     void clean();
     bool setPixel(int x, int y, Rgba color);
+    Rgba getPixel(int x, int y);
     bool isIn(int2 point);
 private:
     int _width;

src/common.h

@@ -65,6 +65,7 @@ struct tvec2 {
 
 typedef tvec2<float> float2;
 typedef tvec2<int> int2;
+typedef unsigned char           byte;
 
 #endif /* COMMON_H */
 

src/draw_image.cc

@@ -17,15 +17,21 @@ gint width = 800;
 Raster raster(width, height);
 
 void example1() {
-        //画背景
-        Image* image1 = Image::loadFromFile("/home/blobt/Documents/dev/cpp/3dbase/build/bin/image/bg.png");
-        raster.drawImage(0, 0, image1);
-        delete image1;
-    
-        //画前景
-        Image* image2 = Image::loadFromFile("/home/blobt/Documents/dev/cpp/3dbase/build/bin/image/colorKey.bmp");
-        raster.drawImageWithKey(200, 250, image2, Rgba(255, 0, 0));
-        delete image2;
+    //画背景
+    Image* image1 = Image::loadFromFile("/home/blobt/Documents/dev/cpp/3dbase/build/bin/image/bg.png");
+    raster.drawImage(0, 0, image1);
+    delete image1;
+
+    //画前景
+    Image* image2 = Image::loadFromFile("/home/blobt/Documents/dev/cpp/3dbase/build/bin/image/colorKey.bmp");
+    raster.drawImageWithKey(200, 250, image2, Rgba(255, 0, 0));
+    delete image2;
+
+    //画草 
+    Image* image3 = Image::loadFromFile("/home/blobt/Documents/dev/cpp/3dbase/build/bin/image/grass.png");
+    //raster.drawImageAlphaTest(400, 250, image3, 100);
+    raster.drawImageAlphaBlend(400, 250, image3,0.5);
+    delete image3;
 
 }