[examples] Add a spritesheet image reader example

examples/Helpers/SpriteReader.hpp

@@ -0,0 +1,76 @@
+#pragma once
+#include <cmath>
+#include <halp/audio.hpp>
+#include <halp/controls.hpp>
+#include <halp/file_port.hpp>
+#include <halp/meta.hpp>
+#include <halp/sample_accurate_controls.hpp>
+#include <halp/texture.hpp>
+
+#include <QImage>
+
+/** 
+ * An example of how to make an object that reads a sprite from a sprite sheet.
+ * Uses Qt's QImage for image processing but any pull request using a simpler image 
+ * reader such as stb_image will be very welcome!
+ */
+namespace examples::helpers
+{
+struct SpriteReader
+{
+  halp_meta(name, "Spirte reader");
+  halp_meta(c_name, "sprite_reader");
+  halp_meta(category, "GFX");
+  halp_meta(author, "Jean-Michaël Celerier");
+  halp_meta(description, "Loads an image file into a texture");
+  halp_meta(uuid, "b28b0cf5-164b-4aa0-8edd-8830ade702e5");
+
+  struct
+  {
+    struct : halp::file_port<"Image", halp::mmap_file_view>
+    {
+      void update(SpriteReader& r) { r.on_image_changed(); }
+    } img;
+
+    halp::xy_spinboxes_i32<"Sprite size", halp::range{1, 1024, 32}> sz;
+    halp::hslider_f32<"Image count"> percentage;
+  } inputs;
+
+  struct
+  {
+    halp::texture_output<"Out"> tex;
+  } outputs;
+
+  QImage image_data;
+  QImage sprite;
+
+  void on_image_changed()
+  {
+    image_data = QImage(QString::fromUtf8(this->inputs.img.file.filename))
+                     .convertedTo(QImage::Format_RGBA8888);
+  }
+
+  void operator()()
+  {
+    if(image_data.isNull())
+      return;
+
+    const int sprite_w = inputs.sz.value.x;
+    const int sprite_h = inputs.sz.value.y;
+    const QSize img_size = image_data.size();
+    const int columns = std::floor(img_size.width() / float(sprite_w));
+    const int rows = std::floor(img_size.height() / float(sprite_h));
+    if(columns <= 0 || rows <= 0)
+      return;
+
+    const int N = columns * rows;
+    const int cur = std::floor(inputs.percentage * N);
+    const int cur_row = cur / columns;
+    const int cur_col = cur % columns;
+    const QRect rect(cur_col * sprite_w, cur_row * sprite_h, sprite_w, sprite_h);
+    sprite = image_data.copy(rect);
+    sprite.mirror();
+    outputs.tex.texture.update(sprite.bits(), inputs.sz.value.x, inputs.sz.value.y);
+  }
+};
+}