feat: add sd-webui style Hires. fix support (#1451)

src/upscaler.h

@@ -0,0 +1,31 @@
+#ifndef __SD_UPSCALER_H__
+#define __SD_UPSCALER_H__
+
+#include "esrgan.hpp"
+#include "stable-diffusion.h"
+#include "tensor.hpp"
+
+#include <memory>
+#include <string>
+
+struct UpscalerGGML {
+    ggml_backend_t backend    = nullptr;  // general backend
+    ggml_type model_data_type = GGML_TYPE_F16;
+    std::shared_ptr<ESRGAN> esrgan_upscaler;
+    std::string esrgan_path;
+    int n_threads;
+    bool direct   = false;
+    int tile_size = 128;
+
+    UpscalerGGML(int n_threads,
+                 bool direct   = false,
+                 int tile_size = 128);
+
+    bool load_from_file(const std::string& esrgan_path,
+                        bool offload_params_to_cpu,
+                        int n_threads);
+    sd::Tensor<float> upscale_tensor(const sd::Tensor<float>& input_tensor);
+    sd_image_t upscale(sd_image_t input_image, uint32_t upscale_factor);
+};
+
+#endif  // __SD_UPSCALER_H__