Fixes math error for negative numbers during point update

main.go

@@ -24,6 +24,13 @@ type filter struct {
 	val int
 }
 
+type col struct {
+	red		filter
+	green	filter
+	blue	filter
+	alpha filter
+}
+
 type filterState struct {
 	red      filter
 	green    filter
@@ -31,6 +38,7 @@ type filterState struct {
 	alpha    filter
 	location point
 	mode     filter
+	sample   col
 }
 var variables = map[string]int{}
 var tree parser.AST
@@ -82,6 +90,12 @@ func filterImage(path, fname string) {
     filter{255, 0,255},
     point{0,0,imSize.X,imSize.Y},
     filter{3,0,0},
+		col{
+			filter{255, 0, 255},
+			filter{255, 0, 255},
+			filter{255, 0, 255},
+			filter{255, 0, 255},
+		},
   }
 
   fmt.Print("Filtering image... ")
@@ -163,7 +177,7 @@ func procedure(p parser.Procedure) {
       updateRegister(p.Kind, p.Expressions[0])
     }
   case "APY":
-    applyToImage(p.Expressions)
+    applyToImage(p.Expressions, false)
   case "RED":
     if len(p.Expressions) >= 1 {
       fil.red.update(p.Expressions[0])
@@ -187,21 +201,38 @@ func procedure(p parser.Procedure) {
       fil.blue.update(p.Expressions[2])
       fil.alpha.update(p.Expressions[3])
     }
+	case "GET":
+		fil.sample.update()
+	case "PUT":
+		applyToImage(p.Expressions, true)
   }
 }
 
-func applyToImage(exps []parser.Expression) {
+func applyToImage(exps []parser.Expression, useSample bool) {
   var err error
   if len(exps) == 0 {
-    im.SetRGBA(
-      fil.location.x,
-      fil.location.y,
-      color.RGBA{
-        uint8(fil.red.val),
-        uint8(fil.green.val),
-        uint8(fil.blue.val),
-        uint8(fil.alpha.val),
-      })
+		if useSample {
+			im.SetRGBA(
+				fil.location.x,
+				fil.location.y,
+				color.RGBA{
+					uint8(fil.sample.red.val),
+					uint8(fil.sample.green.val),
+					uint8(fil.sample.blue.val),
+					uint8(fil.sample.alpha.val),
+				})
+		
+		} else {
+			im.SetRGBA(
+				fil.location.x,
+				fil.location.y,
+				color.RGBA{
+					uint8(fil.red.val),
+					uint8(fil.green.val),
+					uint8(fil.blue.val),
+					uint8(fil.alpha.val),
+				})
+		}
   } else if len(exps) == 2 {
     endX := exps[0].Opperand
     endY := exps[1].Opperand
@@ -225,10 +256,17 @@ func applyToImage(exps []parser.Expression) {
 		var col color.RGBA
     for y := fil.location.y; y <= endY; y++ {
       for x := fil.location.x; x <= endX; x++ {
-				r = fil.red.val
-				g = fil.green.val
-				b = fil.blue.val
-				a = fil.alpha.val
+				if useSample {
+					r = fil.sample.red.val
+					g = fil.sample.green.val
+					b = fil.sample.blue.val
+					a = fil.sample.alpha.val
+				} else {
+					r = fil.red.val
+					g = fil.green.val
+					b = fil.blue.val
+					a = fil.alpha.val
+				}
 				if fil.mode.val != 0 {
 					col = im.RGBAAt(x, y)
 					// fmt.Printf("Orig: %d, New: %d, Avg: %d\n", col.R, r, avgColor(int(col.R), r))

newtest.frs

@@ -13,14 +13,19 @@ RG2 /2
 
 # Nest loop over y then x axis
 BEG 10
+
   BEG 10
+
     COL +80:*6:-200:-4
     APY +RG2:+RG1
     LOC +RG2:+0
     LOC +RG2:+0
+
   END
+
   LOC +RG2:+RG1
-  LOC +RG2:+RG1
+  LOC +0:+RG1
+
 END
 
 

parser/parser.go

@@ -221,7 +221,7 @@ func (p *Parser) Parse() AST {
 
 func isValidProcedure(p string) bool {
   switch p {
-    case "RG1", "RG2", "LOC", "BEG", "END", "RED",
+    case "RG1", "RG2", "LOC", "BEG", "END", "RED", "GET", "PUT",
     "GRN", "BLU", "APH", "COL", "APY", "MOD", "LOX", "LOY":
       return true
   }

receivers.go

@@ -99,10 +99,20 @@ func (p *point) update(change []parser.Expression) {
 		}
 
 		if *target < 0 {
-			*target = max - *target%max
+			*target = max - (*target * -1 % max)
 		}
 	}
+
 	p.x = totalX
 	p.y = totalY
 }
 
+
+func (c *col) update() {
+	imCol := im.RGBAAt(fil.location.x, fil.location.y)
+	fil.sample.red.val = int(imCol.R)
+	fil.sample.blue.val = int(imCol.B)
+	fil.sample.green.val = int(imCol.B)
+	fil.sample.alpha.val = int(imCol.A)
+
+}

sample_test.frs

@@ -0,0 +1,39 @@
+# This will test image sampling
+
+MOD 0
+
+RG2 HIG
+RG2 /2
+
+LOC 50:37
+
+BEG 50
+  LOC +50:*73
+  BEG 2
+    LOC +1:+0
+    GET
+    PUT +0:+RG2
+  END
+END
+
+MOD 1
+LOC 0:0
+COL 240:50:50:240
+RG1 HIG
+RG1 /10
+APY +WID:+RG1
+
+LOC +5:+1
+MOD 0
+BEG 50
+  LOC *9:+2
+  GET
+  LOC +0:+RG1
+  BEG 50
+    LOC +37:+0
+    PUT +1:+1
+  END
+  LOC +0:-RG1
+END
+
+