From: sgunderson@bigfoot.com <>
Date: Sun, 31 May 2009 14:45:26 +0000 (+0200)
Subject: Add the level bias we're supposed to have.
X-Git-Url: https://git.sesse.net/?p=fjl;a=commitdiff_plain;h=0e688f0b5db93745648802bdf1c96d0d526eb9ff

Add the level bias we're supposed to have.
---

diff --git a/idct_float.c b/idct_float.c
index c8bde1b..ede97cd 100644
--- a/idct_float.c
+++ b/idct_float.c
@@ -157,12 +157,12 @@ void idct_float(const int16_t* input, const void* userdata, uint8_t* output)
 		             temp2);
 		for (unsigned x = 0; x < DCTSIZE; ++x) {
 			const double val = temp2[x];
-			if (val < 0.0) {
+			if (val < -128.0) {
 				output[y * DCTSIZE + x] = 0;
-			} else if (val >= 255.0) {
+			} else if (val >= 127.0) {
 				output[y * DCTSIZE + x] = 255;
 			} else {
-				output[y * DCTSIZE + x] = (uint8_t)(val + 0.5);
+				output[y * DCTSIZE + x] = (uint8_t)(val + 128.5);
 			}
 		}
 	}
diff --git a/idct_imprecise_int.c b/idct_imprecise_int.c
index 6dd6983..7048a66 100644
--- a/idct_imprecise_int.c
+++ b/idct_imprecise_int.c
@@ -14,7 +14,7 @@ struct idct_imprecise_int_userdata {
 };
 
 #define PRECISION 12
-#define ROUND_BIAS (1LL << (PRECISION - 1))
+#define ROUND_BIAS (257LL << (PRECISION - 1))
 
 #define FIX(x) ((int32_t)((x) * (1LL << PRECISION) + 0.5))
 
diff --git a/idct_reference.c b/idct_reference.c
index e710de3..f74ad0b 100644
--- a/idct_reference.c
+++ b/idct_reference.c
@@ -43,7 +43,7 @@ void idct_reference(const int16_t* input, const void* userdata, uint8_t* output)
 
 	for (unsigned y = 0; y < 8; ++y) {
 		for (unsigned x = 0; x < 8; ++x) {
-			double val = temp[y * DCTSIZE + x];
+			double val = temp[y * DCTSIZE + x] + 128.0;
 			if (val < 0.0) {
 				output[y * DCTSIZE + x] = 0;
 			} else if (val >= 255.0) {
diff --git a/idct_test.c b/idct_test.c
index d7b543c..bd39c74 100644
--- a/idct_test.c
+++ b/idct_test.c
@@ -76,8 +76,13 @@ void test_dc_becomes_spread_out(idct_alloc_t* idct_alloc, idct_free_t* idct_free
 
 	void* userdata = idct_alloc(quant);
 
-	for (unsigned i = 0; i < 255*8; ++i) {	
-		uint32_t reference_value = i / 8;
+	for (unsigned i = -255*8; i < 255*16; ++i) {	
+		int reference_value = i / 8 + 128;
+		if (reference_value < 0) {
+			reference_value = 0;
+		} else if (reference_value > 255) {
+			reference_value = 255;
+		}
 		coeff[0] = i;
 
 		(*idct)(coeff, userdata, output);