add imageScaleSTB implement

gframe/image_resizer.cpp

@@ -4,10 +4,113 @@
 #include <omp.h>
 #endif
 
+#define STB_IMAGE_RESIZE2_IMPLEMENTATION
+#include "stb_image_resize2.h"
+
 namespace ygo {
 
 ImageResizer imageResizer;
 
+struct StbSamplerCache {
+	STBIR_RESIZE resize{};
+	int in_w = 0;
+	int in_h = 0;
+	int out_w = 0;
+	int out_h = 0;
+	stbir_pixel_layout layout = STBIR_BGRA;
+	bool samplers_built = false;
+
+	~StbSamplerCache() {
+		if(samplers_built) {
+			stbir_free_samplers(&resize);
+			samplers_built = false;
+		}
+	}
+
+	void reset_if_needed(int new_in_w, int new_in_h, int new_out_w, int new_out_h, stbir_pixel_layout new_layout) {
+		if(new_in_w == in_w && new_in_h == in_h && new_out_w == out_w && new_out_h == out_h && new_layout == layout)
+			return;
+		if(samplers_built) {
+			stbir_free_samplers(&resize);
+			samplers_built = false;
+		}
+		in_w = new_in_w;
+		in_h = new_in_h;
+		out_w = new_out_w;
+		out_h = new_out_h;
+		layout = new_layout;
+		resize = STBIR_RESIZE{};
+	}
+};
+
+/** Scale image using stb_image_resize2.
+ * Returns true on success, false on failure or unsupported format. */
+bool ImageResizer::imageScaleSTB(irr::video::IImage* src, irr::video::IImage* dest) {
+	if(!src || !dest)
+		return false;
+
+	const auto srcDim = src->getDimension();
+	const auto destDim = dest->getDimension();
+	if(srcDim.Width == 0 || srcDim.Height == 0 || destDim.Width == 0 || destDim.Height == 0)
+		return false;
+	if(src->getColorFormat() != dest->getColorFormat())
+		return false;
+
+	stbir_pixel_layout layout = STBIR_BGRA;
+	// Fast-paths (8-bit per channel only):
+	// - ECF_A8R8G8B8: Irrlicht stores as BGRA in memory on little-endian.
+	// - ECF_R8G8B8: common for JPEGs (3 channels).
+	switch(src->getColorFormat()) {
+	case irr::video::ECF_A8R8G8B8:
+		layout = STBIR_BGRA;
+		break;
+	case irr::video::ECF_R8G8B8:
+		layout = STBIR_RGB;
+		break;
+	default:
+		return false;
+	}
+
+	void* srcPtr = src->lock();
+	if(!srcPtr)
+		return false;
+	void* destPtr = dest->lock();
+	if(!destPtr) {
+		src->unlock();
+		return false;
+	}
+
+	const int srcStride = (int)src->getPitch();
+	const int destStride = (int)dest->getPitch();
+
+	thread_local StbSamplerCache cache;
+	cache.reset_if_needed((int)srcDim.Width, (int)srcDim.Height, (int)destDim.Width, (int)destDim.Height, layout);
+
+	if(!cache.samplers_built) {
+		stbir_resize_init(&cache.resize,
+						  srcPtr, (int)srcDim.Width, (int)srcDim.Height, srcStride,
+						  destPtr, (int)destDim.Width, (int)destDim.Height, destStride,
+						  layout, STBIR_TYPE_UINT8);
+		stbir_set_edgemodes(&cache.resize, STBIR_EDGE_CLAMP, STBIR_EDGE_CLAMP);
+		// Use box filters to reduce aliasing when downscaling.
+		stbir_set_filters(&cache.resize, STBIR_FILTER_BOX, STBIR_FILTER_BOX);
+		cache.samplers_built = (stbir_build_samplers(&cache.resize) != 0);
+		if(!cache.samplers_built) {
+			dest->unlock();
+			src->unlock();
+			return false;
+		}
+	} else {
+		// Reuse samplers but update buffer pointers for the current images
+		stbir_set_buffer_ptrs(&cache.resize, srcPtr, srcStride, destPtr, destStride);
+	}
+
+	const int ok = stbir_resize_extended(&cache.resize);
+	dest->unlock();
+	src->unlock();
+	return ok != 0;
+}
+
 /** Scale image using nearest neighbor anti-aliasing.
  * Function by Warr1024, from https://github.com/minetest/minetest/issues/2419, modified. */
 void ImageResizer::imageScaleNNAA(irr::video::IImage* src, irr::video::IImage* dest, bool use_threading) {
@@ -88,6 +191,8 @@ void ImageResizer::imageScaleNNAA(irr::video::IImage* src, irr::video::IImage* d
 }
 
 void ImageResizer::resize(irr::video::IImage* src, irr::video::IImage* dest, bool use_threading) {
+	if(imageScaleSTB(src, dest))
+		return;
 	imageScaleNNAA(src, dest, use_threading);
 }
 

gframe/image_resizer.h

@@ -7,6 +7,7 @@ namespace ygo {
 
 class ImageResizer {
 private:
+	bool imageScaleSTB(irr::video::IImage* src, irr::video::IImage* dest);
 	void imageScaleNNAA(irr::video::IImage* src, irr::video::IImage* dest, bool use_threading);
 public:
 	void resize(irr::video::IImage* src, irr::video::IImage* dest, bool use_threading);