From e579ba8ee85b70b3eff08fae6952a8cc10dc0c28 Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Thu, 30 Oct 2025 17:14:31 -0500
Subject: [PATCH] GUI: add option to offset sample

in the amplify one
---
 src/gui/gui.cpp        |  1 +
 src/gui/gui.h          |  2 +-
 src/gui/sampleEdit.cpp | 13 ++++++++++---
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 98a1e921a..53db802cc 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -9017,6 +9017,7 @@ FurnaceGUI::FurnaceGUI():
   resampleTarget(32000),
   resampleStrat(5),
   amplifyVol(100.0),
+  amplifyOff(0.0),
   sampleSelStart(-1),
   sampleSelEnd(-1),
   sampleInfo(true),
diff --git a/src/gui/gui.h b/src/gui/gui.h
index 10f23d976..c606c07fd 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -2621,7 +2621,7 @@ class FurnaceGUI {
   int resizeSize, silenceSize;
   double resampleTarget;
   int resampleStrat;
-  float amplifyVol;
+  float amplifyVol, amplifyOff;
   int sampleSelStart, sampleSelEnd;
   bool sampleInfo, sampleCompatRate;
   bool sampleDragActive, sampleDragMode, sampleDrag16, sampleZoomAuto;
diff --git a/src/gui/sampleEdit.cpp b/src/gui/sampleEdit.cpp
index 441c0294a..bf2152aa2 100644
--- a/src/gui/sampleEdit.cpp
+++ b/src/gui/sampleEdit.cpp
@@ -1212,7 +1212,7 @@ void FurnaceGUI::drawSampleEdit() {
       sameLineMaybe();
       ImGui::Button(ICON_FA_VOLUME_UP "##SAmplify");
       if (ImGui::IsItemHovered()) {
-        ImGui::SetTooltip(_("Amplify"));
+        ImGui::SetTooltip(_("Amplify/Offset"));
       }
       if (openSampleAmplifyOpt) {
         openSampleAmplifyOpt=false;
@@ -1226,6 +1226,11 @@ void FurnaceGUI::drawSampleEdit() {
         }
         ImGui::SameLine();
         ImGui::Text("(%.1fdB)",20.0*log10(amplifyVol/100.0f));
+        ImGui::Text(_("DC offset"));
+        if (ImGui::InputFloat("##Offset",&amplifyOff,-100.0,100.0,"%g%%")) {
+          if (amplifyOff<-100) amplifyOff=-100;
+          if (amplifyOff>100) amplifyOff=100;
+        }
         if (ImGui::Button(_("Apply"))) {
           sample->prepareUndo(true);
           e->lockEngine([this,sample]() {
@@ -1233,15 +1238,17 @@ void FurnaceGUI::drawSampleEdit() {
             float vol=amplifyVol/100.0f;
 
             if (sample->depth==DIV_SAMPLE_DEPTH_16BIT) {
+              float off=32767.0f*(amplifyOff/100.0f);
               for (unsigned int i=start; i<end; i++) {
-                float val=sample->data16[i]*vol;
+                float val=off+sample->data16[i]*vol;
                 if (val<-32768) val=-32768;
                 if (val>32767) val=32767;
                 sample->data16[i]=val;
               }
             } else if (sample->depth==DIV_SAMPLE_DEPTH_8BIT) {
+              float off=127.0f*(amplifyOff/100.0f);
               for (unsigned int i=start; i<end; i++) {
-                float val=sample->data8[i]*vol;
+                float val=off+sample->data8[i]*vol;
                 if (val<-128) val=-128;
                 if (val>127) val=127;
                 sample->data8[i]=val;