Improve tests using structural similarity index (SSI) to calculate si…

…milarity between test image and aolden images

lib/impl/macos/quartz2d/font.mm

@@ -9,6 +9,8 @@
 #include <sstream>
 #include <cmath>
 #include "osx_utils.hpp"
+#include <infra/assert.hpp>
+#include <artist/resources.hpp>
 
 namespace cycfi::artist
 {

lib/impl/macos/quartz2d/image.mm

@@ -105,15 +105,46 @@
    {
       auto path = [NSString stringWithUTF8String : std::string{path_}.c_str() ];
       auto image = (__bridge NSImage*) _impl;
-      auto ref = [image CGImageForProposedRect : nullptr
-                                       context : nullptr
-                                         hints : nullptr];
-      auto* rep = [[NSBitmapImageRep alloc] initWithCGImage : ref];
-      [rep setSize:[image size]];
-
-      auto* data = [rep representationUsingType : NSBitmapImageFileTypePNG
-                                     properties : @{}];
-      [data writeToFile : path atomically : YES];
+
+      // Get the size of the original image
+      NSSize imageSize = [image size];
+
+      // Create an NSBitmapImageRep with the same dimensions as the original image
+      NSBitmapImageRep *bitmapRep = [[NSBitmapImageRep alloc]
+         initWithBitmapDataPlanes : NULL
+         pixelsWide : imageSize.width
+         pixelsHigh : imageSize.height
+         bitsPerSample : 8
+         samplesPerPixel : 4  // RGBA format
+         hasAlpha : YES
+         isPlanar : NO
+         colorSpaceName : NSDeviceRGBColorSpace
+         bytesPerRow : 0
+         bitsPerPixel : 0
+      ];
+
+      // Set the properties for the PNG file
+      NSDictionary *properties = @{
+         NSImageCompressionFactor :  @1.0, // Compression factor (1.0 means no compression)
+         NSImageColorSyncProfileData :  [NSNull null], // No color profile
+         NSImageInterlaced :  @NO // Non-interlaced
+      };
+
+      // Set the current graphics context to the NSBitmapImageRep
+      [NSGraphicsContext saveGraphicsState];
+      [NSGraphicsContext setCurrentContext : [NSGraphicsContext graphicsContextWithBitmapImageRep : bitmapRep]];
+
+      // Draw the original image onto the NSBitmapImageRep
+      [image drawAtPoint : NSZeroPoint fromRect : NSZeroRect operation : NSCompositingOperationCopy fraction : 1.0];
+
+      // Restore the graphics state
+      [NSGraphicsContext restoreGraphicsState];
+
+      // Convert the NSBitmapImageRep to NSData with PNG format
+      NSData* data = [bitmapRep representationUsingType : NSBitmapImageFileTypePNG properties : properties];
+
+      // Write the data to the file
+     [data writeToFile : path atomically : YES];
    }
 
    uint32_t* image::pixels()

test/CMakeLists.txt

@@ -5,12 +5,26 @@
 ###############################################################################
 project(artist_test)
 
+file(
+   GLOB artist_fonts ${CMAKE_CURRENT_LIST_DIR}/../resources/fonts/*.*
+)
+
 if (APPLE)
 
-   add_executable(
-      artist_test MACOSX_BUNDLE
-      main.cpp
-   )
+   if (ARTIST_QUARTZ_2D)
+      add_executable(
+         artist_test MACOSX_BUNDLE
+         main.cpp
+         detail/osx_init.mm
+         ${artist_fonts}
+      )
+   else()
+      add_executable(
+         artist_test MACOSX_BUNDLE
+         main.cpp
+         ${artist_fonts}
+      )
+   endif()
 
    if (ARTIST_QUARTZ_2D)
       file(

test/detail/osx_init.mm

@@ -0,0 +1,72 @@
+/*=============================================================================
+   Copyright (c) 2016-2023 Joel de Guzman
+
+   Distributed under the MIT License [ https://opensource.org/licenses/MIT ]
+=============================================================================*/
+#include <Quartz/Quartz.h>
+#include <dlfcn.h>
+#include <infra/assert.hpp>
+#include <artist/resources.hpp>
+
+///////////////////////////////////////////////////////////////////////////////
+namespace
+{
+   namespace fs = cycfi::fs;
+
+   CFBundleRef get_bundle_from_executable(const char* filepath)
+   {
+      NSString* exec_str = [NSString stringWithCString:filepath encoding : NSUTF8StringEncoding];
+      NSString* mac_os_str = [exec_str stringByDeletingLastPathComponent];
+      NSString* contents_str = [mac_os_str stringByDeletingLastPathComponent];
+      NSString* bundleStr = [contents_str stringByDeletingLastPathComponent];
+      return CFBundleCreate(0, (CFURLRef)[NSURL fileURLWithPath:bundleStr isDirectory : YES]);
+   }
+
+   CFBundleRef get_current_bundle()
+   {
+      Dl_info info;
+      if (dladdr((const void*)get_current_bundle, &info) && info.dli_fname)
+         return get_bundle_from_executable(info.dli_fname);
+      return 0;
+   }
+
+   void activate_font(fs::path font_path)
+   {
+      auto furl = [NSURL fileURLWithPath : [NSString stringWithUTF8String : font_path.c_str()]];
+      CYCFI_ASSERT(furl, "Error: Unexpected missing font.");
+
+      CFErrorRef error = nullptr;
+      CTFontManagerRegisterFontsForURL((__bridge CFURLRef) furl, kCTFontManagerScopeProcess, &error);
+   }
+
+   void get_resource_path(char resource_path[])
+   {
+      CFBundleRef main_bundle = get_current_bundle();
+      CFURLRef resources_url = CFBundleCopyResourcesDirectoryURL(main_bundle);
+      CFURLGetFileSystemRepresentation(resources_url, TRUE, (UInt8*) resource_path, PATH_MAX);
+      CFRelease(resources_url);
+      CFRelease(main_bundle);
+   }
+}
+
+struct resource_setter
+{
+   resource_setter();
+};
+
+resource_setter::resource_setter()
+{
+   // Before anything else, set the working directory so we can access
+   // our resources
+   char resource_path[PATH_MAX];
+   get_resource_path(resource_path);
+   cycfi::artist::add_search_path(resource_path);
+
+   // Load the user fonts from the Resource folder. Normally this is automatically
+   // done on application startup, but for plugins, we need to explicitly load
+   // the user fonts ourself.
+   for (fs::directory_iterator it{resource_path}; it != fs::directory_iterator{}; ++it)
+      if (it->path().extension() == ".ttf")
+         activate_font(it->path());
+}
+

test/main.cpp

@@ -13,6 +13,8 @@
 #include <infra/catch.hpp>
 #include <artist/affine_transform.hpp>
 #include "app_paths.hpp"
+#include <cmath>
+#include <cstdint>
 
 using namespace cycfi::artist;
 using namespace font_constants;
@@ -21,6 +23,15 @@ using cycfi::codepoint;
 auto constexpr window_size = point{640.0f, 480.0f};
 auto constexpr bkd_color = rgba(54, 52, 55, 255);
 
+#if defined(ARTIST_QUARTZ_2D)
+   // Initialize the fonts and resources
+   struct resource_setter
+   {
+      resource_setter();
+   };
+   static resource_setter init_resources;
+#endif
+
 void background(canvas& cnv)
 {
    cnv.add_rect({{0, 0}, window_size});
@@ -231,19 +242,82 @@ void test_draw(canvas& cnv)
    line_styles(cnv);
 }
 
-float diff_pixel(uint32_t a, uint32_t b)
+// Function to extract RGBA values with generic component names Note: Using
+// generic names (x, y, z, w) to make the code agnostic about the order of
+// components within uint32_t values.
+void extract_rgba(uint32_t pixel, uint8_t& x, uint8_t& y, uint8_t& z, uint8_t& w)
 {
-   auto a1 = a & 0xff;
-   auto a2 = (a >> 8) & 0xff;
-   auto a3 = (a >> 16) & 0xff;
-   auto a4 = (a >> 24) & 0xff;
+   x = (pixel >> 24) & 0xFF;
+   y = (pixel >> 16) & 0xFF;
+   z = (pixel >> 8) & 0xFF;
+   w = pixel & 0xFF;
+}
+
+// Function to calculate structural similarity index (SSI) between two images
+double calculate_ssi(uint32_t const  img1[], uint32_t const img2[], int const width, int const height)
+{
+   const double c1 = 0.0001; // Small constant to avoid division by zero
+   const double c2 = 0.0009; // Small constant to avoid division by zero
+   double mean_x = 0.0, mean_y = 0.0, sigma_x = 0.0, sigma_y = 0.0, sigma_xy = 0.0;
+
+   for (int i = 0; i < width * height; ++i)
+   {
+      // Extract individual components using generic names x, y, z, w
+      uint8_t x1, y1, z1, w1;
+      uint8_t x2, y2, z2, w2;
+
+      extract_rgba(img1[i], x1, y1, z1, w1);
+      extract_rgba(img2[i], x2, y2, z2, w2);
+
+      mean_x += x1 + y1 + z1 + w1;
+      mean_y += x2 + y2 + z2 + w2;
+   }
+
+   mean_x /= (width * height * 4);
+   mean_y /= (width * height * 4);
+
+   for (int i = 0; i < width * height; ++i)
+   {
+      // Extract individual components using generic names x, y, z, w
+      uint8_t x1, y1, z1, w1;
+      uint8_t x2, y2, z2, w2;
+
+      extract_rgba(img1[i], x1, y1, z1, w1);
+      extract_rgba(img2[i], x2, y2, z2, w2);
+
+      double dev_x = x1 - mean_x;
+      double dev_y = x2 - mean_y;
+      sigma_x += dev_x * dev_x;
+      sigma_y += dev_y * dev_y;
+      sigma_xy += dev_x * dev_y;
+
+      dev_x = y1 - mean_x;
+      dev_y = y2 - mean_y;
+      sigma_x += dev_x * dev_x;
+      sigma_y += dev_y * dev_y;
+      sigma_xy += dev_x * dev_y;
+
+      dev_x = z1 - mean_x;
+      dev_y = z2 - mean_y;
+      sigma_x += dev_x * dev_x;
+      sigma_y += dev_y * dev_y;
+      sigma_xy += dev_x * dev_y;
+
+      dev_x = w1 - mean_x;
+      dev_y = w2 - mean_y;
+      sigma_x += dev_x * dev_x;
+      sigma_y += dev_y * dev_y;
+      sigma_xy += dev_x * dev_y;
+   }
+
+   sigma_x /= (width * height * 4 - 1);
+   sigma_y /= (width * height * 4 - 1);
+   sigma_xy /= (width * height * 4 - 1);
 
-   auto b1 = b & 0xff;
-   auto b2 = (b >> 8) & 0xff;
-   auto b3 = (b >> 16) & 0xff;
-   auto b4 = (b >> 24) & 0xff;
+   const double numerator = (2 * mean_x * mean_y + c1) * (2 * sigma_xy + c2);
+   const double denominator = (mean_x * mean_x + mean_y * mean_y + c1) * (sigma_x + sigma_y + c2);
 
-   return float(a1-b1) + float(a2-b2) + float(a3-b3) + float(a4-b4);
+   return numerator / denominator;
 }
 
 void compare_golden(image const& pm, std::string name)
@@ -265,10 +339,9 @@ void compare_golden(image const& pm, std::string name)
    REQUIRE(a != nullptr);
    REQUIRE(b != nullptr);
 
-   auto diff = 0;
-   for (auto i = 0; i != (bm_size.x * bm_size.y); ++i)
-      diff += diff_pixel(a[i], b[i]);
-   CHECK(diff == 0);
+   auto ssi = calculate_ssi(a, b, bm_size.x, bm_size.y);
+   CHECK(ssi > 0.995);
+   std::cout << "SSI result for " << name << " : " << ssi << std::endl;
 }
 
 void typography(canvas& cnv)