Beginning of a more sophisticated resample algorithm, starting with calculating filter contributions per scan line.

tests/resample_test.cpp

@@ -0,0 +1,68 @@
+#ifdef _WIN32
+#define STBR_ASSERT(x) \
+	if (!(x)) \
+		__debugbreak();
+#endif
+
+#define STB_RESAMPLE_IMPLEMENTATION
+#define STB_RESAMPLE_STATIC
+#include "stb_resample.h"
+
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+#include "stb_image_write.h"
+
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
+#ifdef _WIN32
+#include <sys/timeb.h>
+#endif
+
+int main(int argc, char** argv)
+{
+	unsigned char* input_data;
+	unsigned char* output_data;
+	int w, h;
+	int n;
+	int out_w, out_h, out_stride;
+
+	if (argc <= 1)
+	{
+		printf("No input image\n");
+		return 1;
+	}
+
+	input_data = stbi_load(argv[1], &w, &h, &n, 0);
+	if (!input_data)
+	{
+		printf("Input image could not be loaded");
+		return 1;
+	}
+
+	out_w = 1024;
+	out_h = 1024;
+	out_stride = (out_w + 10) * n;
+
+	output_data = (unsigned char*)malloc(out_stride * out_h);
+
+	int in_w = 512;
+	int in_h = 512;
+
+	size_t memory_required = stbr_calculate_memory(in_w, in_h, w*n, out_w, out_h, out_stride, n, STBR_FILTER_NEAREST);
+	void* extra_memory = malloc(memory_required);
+
+	// Cut out the outside 64 pixels all around to test the stride.
+	int border = 64;
+	STBR_ASSERT(in_w + border <= w);
+	STBR_ASSERT(in_h + border <= h);
+
+	stbr_resize_arbitrary(input_data + w * border * n + border * n, in_w, in_h, w*n, output_data, out_w, out_h, out_stride, n, STBR_TYPE_UINT8, STBR_FILTER_NEAREST, extra_memory, memory_required);
+
+	free(extra_memory);
+
+	stbi_write_png("output.png", out_w, out_h, n, output_data, out_stride);
+
+	free(output_data);
+
+	return 0;
+}