fix BC1 compressor

1 files changed, 55 insertions, 21 deletions

diff --git a/convtexture.c b/convtexture.c
index a04e3c9..2670b59 100644
--- a/convtexture.c
+++ b/convtexture.c
@@ -29,10 +29,19 @@ const char* format_names[] = {
 #undef x
 };
 
+unsigned encode_endpoint(const vec3* v) {
+	return
+		((unsigned)(v->r * 31.9999f) << 11) |
+		((unsigned)(v->g * 63.9999f) << 5) |
+		((unsigned)(v->b * 31.9999f));
+}
+
 void get_block(Block* block, Colour* pixels, int stride) {
 	int x, y, i;
 	vec3 cols[4 * 4];
+	vec3 palette[3];
 	vec3 s, e;
+	unsigned es, ee;
 	float cd;
 	for (y = 0; y < 4; y++) {
 		for (x = 0; x < 4; x++) {
@@ -61,19 +70,48 @@ void get_block(Block* block, Colour* pixels, int stride) {
 			}
 		}
 	}
+	es = encode_endpoint(&s);
+	ee = encode_endpoint(&e);
+	if (es == ee) {
+		block->start = s;
+		block->end.r = 0.0f;
+		block->end.g = 0.0f;
+		block->end.b = 0.0f;
+		for (i = 0; i < 16; i++) {
+			block->indices[i] = 0;
+		}
+		return;
+	}
+	if (es < ee) {
+		/* todo alpha */
+		vec3 t = s;
+		s = e;
+		e = t;
+	}
+	palette[0] = s;
+	palette[1] = e;
+	palette[2].r = 0.666666f*palette[0].r + 0.333333f*palette[1].r;
+	palette[2].g = 0.666666f*palette[0].g + 0.333333f*palette[1].g;
+	palette[2].b = 0.666666f*palette[0].b + 0.333333f*palette[1].b;
+	palette[3].r = 0.333333f*palette[0].r + 0.666666f*palette[1].r;
+	palette[3].g = 0.333333f*palette[0].g + 0.666666f*palette[1].g;
+	palette[3].b = 0.333333f*palette[0].b + 0.666666f*palette[1].b;
 	for (i = 0; i < 4 * 4; i++) {
 		vec3* col = &cols[i];
-		float d;
-		d =
-			(e.r - col->r) * (e.r - col->r) +
-			(e.g - col->g) * (e.g - col->g) +
-			(e.b - col->b) * (e.b - col->b);
-		if (cd < 0.0001f)
-			block->indices[i] = 0;
-		else {
-			d = d / cd;
-			block->indices[i] = (int)((1.0f - d) * 3.1f);
+		int closest = 0, j;
+		float cd = 99999.0f;
+		for (j = 0; j < 4; j++) {
+			vec3* p = &palette[j];
+			float d =
+				(p->r - col->r) * (p->r - col->r) +
+				(p->g - col->g) * (p->g - col->g) +
+				(p->b - col->b) * (p->b - col->b);
+			if (d < cd) {
+				cd = d;
+				closest = j;
+			}
 		}
+		block->indices[i] = closest;
 	}
 	block->start = s;
 	block->end = e;
@@ -81,19 +119,15 @@ void get_block(Block* block, Colour* pixels, int stride) {
 
 void compress_block(const Block* block, FILE* f) {
 	int i;
-	unsigned start =
-		((unsigned)(block->start.r * 31.9999f) << 11) |
-		((unsigned)(block->start.g * 63.9999f) << 5) |
-		((unsigned)(block->start.b * 31.9999f));
-	unsigned end =
-		((unsigned)(block->end.r * 31.9999f) << 11) |
-		((unsigned)(block->end.g * 63.9999f) << 5) |
-		((unsigned)(block->end.b * 31.9999f));
-	unsigned palette = (start << 16) | end;
+	unsigned start = encode_endpoint(&block->start);
+	unsigned end   = encode_endpoint(&block->end);
 	unsigned indices = 0;
-	fwrite(&palette, 1, 4, f);
+	fwrite(&start, 1, 2, f);
+	fwrite(&end,   1, 2, f);
 	for (i = 0; i < 4 * 4; i++) {
-		indices |= block->indices[i] << (i * 2);
+		int idx = (4 * 4 - 1) - i;
+		idx = i;
+		indices |= block->indices[i] << (idx * 2);
 	}
 	fwrite(&indices, 1, 4, f);
 }