Make ImageWriter an abstract base class; add PngImageWriter

src/fart/ImageWriter.cpp

@@ -1,51 +1,15 @@
 #include <fart/ImageWriter.h>
-#include <png.h>
+#include <fart/PngImageWriter.h>
-#include <stdint.h>
 #include <stdio.h>
-#include <algorithm>
-#include <cmath>
 #include <filesystem>
-#include <vector>
 
-static uint8_t to_byte(double v)
+ImageWriter * ImageWriter::build(const std::string & fname)
-{
-    return (uint8_t)std::lround(std::clamp(v, 0.0, 1.0) * 255.0);
-}
-
-static bool write_png(const Image & image, const std::string & fname)
-{
-    std::vector<uint8_t> buffer(image.width * image.height * 4u);
-    for (size_t i = 0u; i < image.pixels.size(); i++)
-    {
-        const Color & c = image.pixels[i];
-        buffer[i * 4u + 0u] = to_byte(c.r);
-        buffer[i * 4u + 1u] = to_byte(c.g);
-        buffer[i * 4u + 2u] = to_byte(c.b);
-        buffer[i * 4u + 3u] = to_byte(c.a);
-    }
-
-    png_image png = {};
-    png.version = PNG_IMAGE_VERSION;
-    png.width = image.width;
-    png.height = image.height;
-    png.format = PNG_FORMAT_RGBA;
-
-    if (!png_image_write_to_file(&png, fname.c_str(), 0, buffer.data(), 0, nullptr))
-    {
-        fprintf(stderr, "Error writing PNG file '%s': %s\n", fname.c_str(), png.message);
-        png_image_free(&png);
-        return false;
-    }
-    return true;
-}
-
-bool ImageWriter::write(const Image & image, const std::string & fname)
 {
     std::string ext = std::filesystem::path(fname).extension().string();
     if (ext == ".png")
     {
-        return write_png(image, fname);
+        return new PngImageWriter(fname);
     }
     fprintf(stderr, "Unsupported output image format: '%s'\n", fname.c_str());
-    return false;
+    return nullptr;
 }

src/fart/ImageWriter.h

@@ -6,5 +6,11 @@
 class ImageWriter
 {
 public:
-    static bool write(const Image & image, const std::string & fname);
+    static ImageWriter * build(const std::string & fname);
+    virtual ~ImageWriter() = default;
+    virtual bool write(const Image & image) = 0;
+
+protected:
+    ImageWriter(const std::string & fname) : fname(fname) {}
+    std::string fname;
 };

src/fart/PngImageWriter.cpp

@@ -0,0 +1,39 @@
+#include <fart/PngImageWriter.h>
+#include <png.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <algorithm>
+#include <cmath>
+#include <vector>
+
+static uint8_t to_byte(double v)
+{
+    return (uint8_t)std::lround(std::clamp(v, 0.0, 1.0) * 255.0);
+}
+
+bool PngImageWriter::write(const Image & image)
+{
+    std::vector<uint8_t> buffer(image.width * image.height * 4u);
+    for (size_t i = 0u; i < image.pixels.size(); i++)
+    {
+        const Color & c = image.pixels[i];
+        buffer[i * 4u + 0u] = to_byte(c.r);
+        buffer[i * 4u + 1u] = to_byte(c.g);
+        buffer[i * 4u + 2u] = to_byte(c.b);
+        buffer[i * 4u + 3u] = to_byte(c.a);
+    }
+
+    png_image png = {};
+    png.version = PNG_IMAGE_VERSION;
+    png.width = image.width;
+    png.height = image.height;
+    png.format = PNG_FORMAT_RGBA;
+
+    if (!png_image_write_to_file(&png, fname.c_str(), 0, buffer.data(), 0, nullptr))
+    {
+        fprintf(stderr, "Error writing PNG file '%s': %s\n", fname.c_str(), png.message);
+        png_image_free(&png);
+        return false;
+    }
+    return true;
+}

src/fart/PngImageWriter.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <fart/ImageWriter.h>
+
+class PngImageWriter : public ImageWriter
+{
+public:
+    PngImageWriter(const std::string & fname) : ImageWriter(fname) {}
+    bool write(const Image & image) override;
+};