Prepare STB to use the new version of resize (and fall back to old)

Newer versions of STB don't have the stb_image_resize.h anymore, but
a new stb_image_resize2.h with slightly different function names.
Use the new one if available, and provide adapter functions to work
in both cases.

src/CMakeLists.txt

@@ -101,13 +101,18 @@ if(WITH_VIDEO_DECODING)
 endif()
 
 if(WITH_STB_IMAGE)
+  # STB usuall does not come with pkg-config. Just check if we see the include
   include(CheckIncludeFileCXX)
   CHECK_INCLUDE_FILE_CXX(stb/stb_image.h HAVE_STB)
   target_sources(timg PUBLIC stb-image-source.h stb-image-source.cc)
   if(NOT HAVE_STB)
     message("--> Using STB from third_party/ instead")
     target_include_directories(timg PRIVATE ${CMAKE_SOURCE_DIR}/third_party)
   endif()
+  CHECK_INCLUDE_FILE_CXX(stb/stb_image_resize2.h STB_RESIZE_VERSION2)
+  if(STB_RESIZE_VERSION2)
+    target_compile_definitions(timg PUBLIC STB_RESIZE_VERSION2)
+  endif()
   target_compile_definitions(timg PUBLIC WITH_TIMG_STB)
 endif()
 
@@ -116,7 +121,7 @@ if(WITH_QOI_IMAGE)
   CHECK_INCLUDE_FILE_CXX(qoi.h HAVE_QOI)
   target_sources(timg PUBLIC qoi-image-source.h qoi-image-source.cc)
   if(NOT HAVE_QOI)
-    message("--> Using OTB from third_party/ instead")
+    message("--> Using QOI from third_party/ instead")
     target_include_directories(timg PRIVATE ${CMAKE_SOURCE_DIR}/third_party/qoi)
   endif()
   target_compile_definitions(timg PUBLIC WITH_TIMG_QOI)

src/stb-image-source.cc

@@ -21,24 +21,45 @@
 #define STB_IMAGE_RESIZE_IMPLEMENTATION
 // Least amount of fuzziness on upscaling
 #define STBIR_DEFAULT_FILTER_UPSAMPLE STBIR_FILTER_BOX
-#include "stb/stb_image_resize.h"
+
+// There is an old and a new version of stb resize. Prefer newer if available
+// (tested for in CMake), and provide adapter functions to use either.
+#if STB_RESIZE_VERSION2
+#    include "stb/stb_image_resize2.h"
+inline void stb_resize_image(const unsigned char *input_pixels, int input_w,
+                             int input_h, unsigned char *output_pixels,
+                             int output_w, int output_h) {
+    static constexpr stbir_pixel_layout kFramebufferFormat = STBIR_RGBA;
+    stbir_resize_uint8_linear(input_pixels, input_w, input_h, 0,  //
+                              output_pixels, output_w, output_h, 0,
+                              kFramebufferFormat);
+}
+
+#else
+#    include "stb/stb_image_resize.h"
+inline void stb_resize_image(const unsigned char *input_pixels, int input_w,
+                             int input_h, unsigned char *output_pixels,
+                             int output_w, int output_h) {
+    static constexpr int kFramebufferFormat = 4;  // RGBA.
+    stbir_resize_uint8(input_pixels, input_w, input_h, 0,     //
+                       output_pixels, output_w, output_h, 0,  //
+                       kFramebufferFormat);
+}
+#endif
 
 // TODO: preprocessed frame and SendFrames() are similar to
 // image-display.cc. Maybe things can be consolidated.
 
-// Normalize on RGBA, so that it fits our Framebuffer format.
-static constexpr int kDesiredChannels = 4;
-
+static constexpr int kDesiredChannels = 4;  // RGBA, our framebuffer format
 namespace timg {
 class STBImageSource::PreprocessedFrame {
 public:
     PreprocessedFrame(const uint8_t *image_data, int source_w, int source_h,
                       int target_w, int target_h, const Duration &delay,
                       const DisplayOptions &opt)
         : delay_(delay), framebuffer_(target_w, target_h) {
-        stbir_resize_uint8(image_data, source_w, source_h, 0,
-                           (uint8_t *)framebuffer_.begin(), target_w, target_h,
-                           0, kDesiredChannels /*RGBA*/);
+        stb_resize_image(image_data, source_w, source_h,
+                         (uint8_t *)framebuffer_.begin(), target_w, target_h);
         framebuffer_.AlphaComposeBackground(
             opt.bgcolor_getter, opt.bg_pattern_color,
             opt.pattern_size * opt.cell_x_px,