Add interpolation and configuration for background gradient

src/main/java/com/tterrag/blurbg/BlurBG.java

@@ -20,6 +20,7 @@ import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.common.config.Configuration;
 import net.minecraftforge.fml.common.Mod;
 import net.minecraftforge.fml.common.Mod.EventHandler;
+import net.minecraftforge.fml.common.Mod.Instance;
 import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;
 import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 import net.minecraftforge.fml.common.gameevent.TickEvent.Phase;
@@ -29,12 +30,17 @@ import net.minecraftforge.fml.relauncher.ReflectionHelper;
 @Mod(modid = "blurbg", name = "BlurBG", version = "@VERSION@", acceptedMinecraftVersions = "[1.9, 1.12)")
 public class BlurBG {
     
+    @Instance
+    public static BlurBG instance;
+    
     private String[] blurExclusions;
 
     private Field _listShaders;
     private long start;
     private int fadeTime;
     
+    private int colorFirst, colorSecond;
+    
     @EventHandler
     public void preInit(FMLPreInitializationEvent event) {
         MinecraftForge.EVENT_BUS.register(this);
@@ -47,6 +53,16 @@ public class BlurBG {
         
         fadeTime = config.getInt("fadeTime", Configuration.CATEGORY_GENERAL, 300, 0, Integer.MAX_VALUE, "The time it takes for the blur to fade in, in ms.");
         
+        colorFirst = Integer.parseUnsignedInt(
+                config.getString("gradientStartColor",  Configuration.CATEGORY_GENERAL, "66000000", "The start color of the background gradient. Given in ARGB hex."),
+                16
+        );
+        
+        colorSecond = Integer.parseUnsignedInt(
+                config.getString("gradientEndColor",    Configuration.CATEGORY_GENERAL, "66000000", "The end color of the background gradient. Given in ARGB hex."),
+                16
+        );
+        
         config.save();
     }
     
@@ -67,6 +83,10 @@ public class BlurBG {
         }
     }
     
+    private float getProgress() {
+        return Math.min((System.currentTimeMillis() - start) / (float) fadeTime, 1);
+    }
+    
     @SuppressWarnings("null")
     @SubscribeEvent
     public void onRenderTick(RenderTickEvent event) {
@@ -78,7 +98,7 @@ public class BlurBG {
                 for (Shader s : shaders) {
                     ShaderUniform su = s.getShaderManager().getShaderUniform("Progress");
                     if (su != null) {
-                        su.set(Math.min((System.currentTimeMillis() - start) / (float) fadeTime, 1));
+                        su.set(getProgress());
                     }
                 }
             } catch (IllegalArgumentException | IllegalAccessException e) {
@@ -86,5 +106,18 @@ public class BlurBG {
             }
         }
     }
-
+    
+    public static int getBackgroundColor(boolean second) {
+        int color = second ? instance.colorSecond : instance.colorFirst;
+        int a = color >> 24;
+        int r = (color >> 16) & 0xFF;
+        int b = (color >> 8) & 0xFF;
+        int g = color & 0xFF;
+        float prog = instance.getProgress();
+        a *= prog;
+        r *= prog;
+        g *= prog;
+        b *= prog;
+        return a << 24 | r << 16 | b << 8 | g;
+    }
 }

src/main/java/com/tterrag/blurbg/BlurBGTransformer.java

@@ -7,7 +7,8 @@ import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.Opcodes;
 import org.objectweb.asm.tree.AbstractInsnNode;
 import org.objectweb.asm.tree.ClassNode;
-import org.objectweb.asm.tree.LdcInsnNode;
+import org.objectweb.asm.tree.InsnNode;
+import org.objectweb.asm.tree.MethodInsnNode;
 import org.objectweb.asm.tree.MethodNode;
 
 import net.minecraft.launchwrapper.IClassTransformer;
@@ -18,6 +19,10 @@ public class BlurBGTransformer implements IClassTransformer {
     
     private static final String DRAW_WORLD_BAGKGROUND_METHOD = "drawWorldBackground";
     private static final String DRAW_WORLD_BAGKGROUND_METHOD_OBF = "func_146270_b";
+    
+    private static final String BLUR_MAIN_CLASS = "com/tterrag/blurbg/BlurBG";
+    private static final String COLOR_HOOK_METHOD_NAME = "getBackgroundColor";
+    private static final String COLOR_HOOK_METHOD_DESC = "(Z)I";
 
     @Override
     public byte[] transform(String name, String transformedName, byte[] basicClass) {
@@ -44,9 +49,17 @@ public class BlurBGTransformer implements IClassTransformer {
 //                            break;
 //                        }
                         if (next.getOpcode() == Opcodes.LDC) {
-                            // TODO make this configurable? 
                             System.out.println("Modifying GUI background darkness... ");
-                            ((LdcInsnNode)next).cst = ((LdcInsnNode)next.getNext()).cst = 0x66000000;
+                            AbstractInsnNode colorHook = new MethodInsnNode(Opcodes.INVOKESTATIC, BLUR_MAIN_CLASS, COLOR_HOOK_METHOD_NAME, COLOR_HOOK_METHOD_DESC, false);
+                            AbstractInsnNode colorHook2 = colorHook.clone(null);
+                            
+                            // Replace LDC with hooks
+                            m.instructions.set(next, colorHook);
+                            m.instructions.set(colorHook.getNext(), colorHook2);
+
+                            // Load boolean constants for method param
+                            m.instructions.insertBefore(colorHook, new InsnNode(Opcodes.ICONST_0));
+                            m.instructions.insertBefore(colorHook2, new InsnNode(Opcodes.ICONST_1));
                             break;
                         }
                     }