Initial release

tests/test_preprocess.cpp

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+// Byte-exactness test of trellis2_preprocess_rgba against the Python
+// reference (PIL): dumps/fixture_rgba.png -> preprocess -> must equal
+// dumps/fixture_512.png (produced by scripts/dump_dino_reference.py).
+//
+// usage: test_preprocess <fixture_rgba.png> <fixture_512.png>
+// exits 77 (ctest SKIP) when inputs are missing.
+
+#include "trellis2.h"
+
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
+#include <cstdio>
+#include <cstdlib>
+#include <fstream>
+#include <string>
+#include <vector>
+
+int main(int argc, char ** argv) {
+    if (argc < 3) {
+        std::fprintf(stderr, "usage: %s <fixture_rgba.png> <fixture_512.png>\n", argv[0]);
+        return 2;
+    }
+    if (!std::ifstream(argv[1]).good() || !std::ifstream(argv[2]).good()) {
+        std::fprintf(stderr, "missing input file(s), skipping\n");
+        return 77;
+    }
+
+    int w = 0, h = 0, comp = 0;
+    unsigned char * rgba = stbi_load(argv[1], &w, &h, &comp, 4);
+    if (!rgba) {
+        std::fprintf(stderr, "decode failed: %s\n", stbi_failure_reason());
+        return 1;
+    }
+
+    int rw = 0, rh = 0, rc = 0;
+    unsigned char * ref = stbi_load(argv[2], &rw, &rh, &rc, 3);
+    if (!ref) {
+        std::fprintf(stderr, "decode failed: %s\n", stbi_failure_reason());
+        stbi_image_free(rgba);
+        return 1;
+    }
+
+    std::string err;
+    std::vector<uint8_t> got;
+    if (!trellis2_preprocess_rgba(rgba, w, h, rw, got, &err)) {
+        std::fprintf(stderr, "preprocess failed: %s\n", err.c_str());
+        return 1;
+    }
+
+    const size_t n = (size_t) rw * rh * 3;
+    size_t n_diff = 0, max_diff = 0, first = 0;
+    for (size_t i = 0; i < n; ++i) {
+        const int d = std::abs((int) got[i] - (int) ref[i]);
+        if (d) {
+            if (!n_diff) first = i;
+            ++n_diff;
+            if ((size_t) d > max_diff) max_diff = (size_t) d;
+        }
+    }
+
+    std::printf("preprocess %dx%d -> %dx%d: %zu/%zu bytes differ (max %zu)\n",
+                w, h, rw, rh, n_diff, n, max_diff);
+    stbi_image_free(rgba);
+    stbi_image_free(ref);
+
+    // Byte-exact is the goal; tolerate nothing so regressions are loud.
+    if (n_diff != 0) {
+        std::printf("first diff at byte %zu\nRESULT: FAIL\n", first);
+        return 1;
+    }
+    std::printf("RESULT: PASS\n");
+    return 0;
+}