Fix inverted resize check

Add a regression test

Author: bouk

apriltag_quad_thresh.c

@@ -1513,7 +1513,7 @@ image_u8_t *threshold_bayer(apriltag_detector_t *td, image_u8_t *im)
 unionfind_t* connected_components(apriltag_detector_t *td, image_u8_t* threshim, int w, int h, int ts) {
     uint32_t maxid = w * h;
     if (td->cached_uf) {
-        if (td->cached_uf->maxid <= maxid) {
+        if (td->cached_uf->maxid >= maxid) {
             unionfind_reset(td->cached_uf);
         } else {
             unionfind_resize(td->cached_uf, maxid);

test/CMakeLists.txt

@@ -48,3 +48,11 @@ endif()
 
 add_test(NAME test_quick_decode COMMAND test_quick_decode)
 
+add_executable(test_multiple_sizes test_multiple_sizes.c)
+target_link_libraries(test_multiple_sizes ${PROJECT_NAME})
+
+add_test(NAME test_multiple_sizes
+         COMMAND $<TARGET_FILE:test_multiple_sizes> data/33369213973_9d9bb4cc96_c.jpg
+         WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+)
+

test/test_multiple_sizes.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <apriltag.h>
+#include <tag36h11.h>
+#include <common/pjpeg.h>
+
+int main(int argc, char *argv[])
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s <image.jpg>\n", argv[0]);
+        return EXIT_FAILURE;
+    }
+
+    pjpeg_t *pjpeg = pjpeg_create_from_file(argv[1], 0, NULL);
+    if (pjpeg == NULL) {
+        fprintf(stderr, "Failed to load %s\n", argv[1]);
+        return EXIT_FAILURE;
+    }
+    image_u8_t *im = pjpeg_to_u8_baseline(pjpeg);
+
+    apriltag_family_t *tf = tag36h11_create();
+    apriltag_detector_t *td = apriltag_detector_create();
+    apriltag_detector_add_family(td, tf);
+    td->refine_edges = false;
+
+    // First detect with quad_decimate=2
+    td->quad_decimate = 2;
+    zarray_t *dets1 = apriltag_detector_detect(td, im);
+    int n1 = zarray_size(dets1);
+    printf("decimate=2: %d detections\n", n1);
+    apriltag_detections_destroy(dets1);
+
+    // Now detect with quad_decimate=1
+    td->quad_decimate = 1;
+    zarray_t *dets2 = apriltag_detector_detect(td, im);
+    int n2 = zarray_size(dets2);
+    printf("decimate=1: %d detections\n", n2);
+    apriltag_detections_destroy(dets2);
+
+    image_u8_destroy(im);
+    pjpeg_destroy(pjpeg);
+    apriltag_detector_destroy(td);
+    apriltag_detector_destroy(td2);
+    tag36h11_destroy(tf);
+
+    if (n2 != n_ref) {
+        fprintf(stderr, "FAIL: decimate 2->1 got %d detections, expected %d\n", n2, n_ref);
+        return EXIT_FAILURE;
+    }
+
+    printf("PASS\n");
+    return EXIT_SUCCESS;
+}