add Canvas constructor & add canvas:blit

src/graphics/core/Atlas.cpp

@@ -97,7 +97,7 @@ std::unique_ptr<Atlas> AtlasBuilder::build(uint extrusion, bool prepare, uint ma
         uint y = rect.y;
         uint w = rect.width;
         uint h = rect.height;
-        canvas->blit(entry.image.get(), rect.x, rect.y);
+        canvas->blit(*entry.image, rect.x, rect.y);
         for (uint j = 0; j < extrusion; j++) {
             canvas->extrude(x - j, y - j, w + j*2, h + j*2);
         }

src/graphics/core/ImageData.cpp

@@ -81,13 +81,13 @@ void ImageData::flipY() {
     }
 }
 
-void ImageData::blit(const ImageData* image, int x, int y) {
-    if (format == image->format) {
+void ImageData::blit(const ImageData& image, int x, int y) {
+    if (format == image.format) {
         blitMatchingFormat(image, x, y);
         return;
     }
     if (format == ImageFormat::rgba8888 && 
-        image->format == ImageFormat::rgb888) {
+        image.format == ImageFormat::rgb888) {
         blitRGB_on_RGBA(image, x, y);
         return;
     }
@@ -187,10 +187,10 @@ void ImageData::drawLine(int x1, int y1, int x2, int y2, const glm::ivec4& color
     }
 }
 
-void ImageData::blitRGB_on_RGBA(const ImageData* image, int x, int y) {
-    ubyte* source = image->getData();
-    uint srcwidth = image->getWidth();
-    uint srcheight = image->getHeight();
+void ImageData::blitRGB_on_RGBA(const ImageData& image, int x, int y) {
+    ubyte* source = image.getData();
+    uint srcwidth = image.getWidth();
+    uint srcheight = image.getHeight();
 
     for (uint srcy = std::max(0, -y);
          srcy < std::min(srcheight, height - y);
@@ -210,7 +210,7 @@ void ImageData::blitRGB_on_RGBA(const ImageData* image, int x, int y) {
     }
 }
 
-void ImageData::blitMatchingFormat(const ImageData* image, int x, int y) {
+void ImageData::blitMatchingFormat(const ImageData& image, int x, int y) {
     uint comps;
     switch (format) {
         case ImageFormat::rgb888: comps = 3; break;
@@ -218,20 +218,24 @@ void ImageData::blitMatchingFormat(const ImageData* image, int x, int y) {
         default:
             throw std::runtime_error("only unsigned byte formats supported");    
     }
-    ubyte* source = image->getData();
-    uint srcwidth = image->getWidth();
-    uint srcheight = image->getHeight();
+    ubyte* source = image.getData();
+
+    const uint width = this->width;
+    const uint height = this->height;
+    const uint src_width = image.getWidth();
+    const uint src_height = image.getHeight();
+    ubyte* data = this->data.get();
 
     for (uint srcy = std::max(0, -y);
-         srcy < std::min(srcheight, height - y);
+         srcy < std::min(src_height, height - y);
          srcy++) {
         for (uint srcx = std::max(0, -x);
-             srcx < std::min(srcwidth, width - x);
+             srcx < std::min(src_width, width - x);
              srcx++) {
             uint dstx = srcx + x;
             uint dsty = srcy + y;
             uint dstidx = (dsty * width + dstx) * comps;
-            uint srcidx = (srcy * srcwidth + srcx) * comps;
+            uint srcidx = (srcy * src_width + srcx) * comps;
             for (uint c = 0; c < comps; c++) {
                 data[dstidx + c] = source[srcidx + c];
             }

src/graphics/core/ImageData.hpp

@@ -15,6 +15,9 @@ class ImageData {
     uint width;
     uint height;
     std::unique_ptr<ubyte[]> data;
+
+    void blitRGB_on_RGBA(const ImageData& image, int x, int y);
+    void blitMatchingFormat(const ImageData& image, int x, int y);
 public:
     ImageData(ImageFormat format, uint width, uint height);
     ImageData(ImageFormat format, uint width, uint height, std::unique_ptr<ubyte[]> data);
@@ -25,9 +28,7 @@ public:
     void flipY();
 
     void drawLine(int x1, int y1, int x2, int y2, const glm::ivec4& color);
-    void blitRGB_on_RGBA(const ImageData* image, int x, int y);
-    void blitMatchingFormat(const ImageData* image, int x, int y);
-    void blit(const ImageData* image, int x, int y);
+    void blit(const ImageData& image, int x, int y);
     void extrude(int x, int y, int w, int h);
     void fixAlphaColor();