I realized that I needed another variable that would keep track of the offset from the origin. In this case, I created variables for the X and Y offsets, and adjusted the view to add the distance of the offset multiplied by the scale. This makes the image center. If we are -20 pixels on the X axis, and 50 pixels on the Y, and 1.4x zoomed in, not only do we need to move the image -20,50, we need to multiply those numbers by the 1.4.

This is really simple, and I thought I was doing it correctly at one point but it wasn't working right. If you keep everything simple and clear, it will work. Check out my fixed code to see the difference in how this works:

1. import processing.opengl.*;
2. 
   
3. PImage enhanceImage;
4. float scalePercent = 1;
5. int imgX = 0;
6. int imgY = 0;
7. int imgXoffset = 0;
8. int imgYoffset = 0;
9. int newX = 0;
10. int newY = 0;
11. 
    
12. 
    
13. boolean moveLeft = false;
14. boolean moveRight = false;
15. boolean moveUp = false;
16. boolean moveDown = false;
17. boolean moveIn = false;
18. boolean moveOut = false;
19. boolean moveStop = true;
20. 
    
21. 
    
22. void setup() {
23. 
    
24.   size(640, 480,OPENGL);
25. 
    
26.   enhanceImage = loadImage("example_image.jpg ");  
27.   
28.   imgX=width/2;
29.   imgY=height/2; 
30.    
31.   startSize(); 
32. 
    
33. }
34. 
    
35. void draw() {
36.   background(0);
37.   
38.   
39.   
40.   imageMode(CENTER);
41.   
42.   newX = int(imgX+(imgXoffset*scalePercent));
43.   newY = int(imgY+(imgYoffset*scalePercent));
44. 
    
45.   pushMatrix(); 
46.   translate(newX,newY);
47.   scale(scalePercent);
48.   image(enhanceImage,0,0);    
49.   popMatrix();
50.   
51.   moveRoutine();
52.   textRoutine();
53.   drawLines();
54. }
55. 
    
56. void moveRoutine(){
57.   
58.  if(moveIn){
59.   moveStop=false; 
60.   
61.   scalePercent+=.01;
62.  } 
63.  if(moveOut){
64.    moveStop=false; 
65.   
66.   scalePercent-=.01; 
67.   
68.  }
69.  if(moveLeft){
70.    moveStop=false; 
71.   imgXoffset--; 
72.  }
73.  if(moveRight){
74.    moveStop=false; 
75.   imgXoffset++; 
76.  }
77.  if(moveUp){
78.    moveStop=false; 
79.   imgYoffset--; 
80.  }
81.  if(moveDown){
82.    moveStop=false; 
83.   imgYoffset++; 
84.  }
85.  if(moveStop){
86.   moveIn = false;
87.   moveOut = false;
88.   moveLeft = false;
89.   moveRight = false;
90.   moveUp = false;
91.   moveDown = false;
92.  }
93.   
94. }
95. 
    
96. void textRoutine(){
97.   
98.   text(imgX + "x, " + imgY + "y" + imgXoffset + "xoffset, " + imgYoffset + "yoffset", width/2, height-20);
99.   
100. }
101. 
     
102. void drawLines(){
103.  line(width/2,0,width/2,height);
104.  line(0,height/2,width,height/2);
105.   
106. }
107. 
     
108. 
     
109. void startSize(){
110.   
111. float originalWidth = enhanceImage.width;
112. float originalHeight = enhanceImage.height;
113. float tempscalePercent;
114. 
     
115. 
     
116. if (originalWidth>originalHeight){
117. scalePercent = width/originalWidth;
118.  //image width in relation to scene width = scale percentage
119.  
120. }
121. else if (originalWidth<=originalHeight){
122. scalePercent = height/originalHeight; 
123.  println(scalePercent);
124. }
125. 
     
126.   
127. }
128. 
     
129. 
     
130. 
     
131. void keyPressed() {
132.   
133.   if (key == 'e') {
134.     moveIn=true;
135.     //scalePercent+=.01;
136.   }
137.   
138.   if (key == 'w') {
139.     moveOut=true;
140.     //scalePercent-=.01;
141.   }
142.   
143.   if(key == ' '){
144.       moveStop=true;
145.       
146.       
147.       moveIn = false;
148.       moveOut = false;
149.       moveLeft = false;
150.       moveRight = false;
151.       moveUp = false;
152.       moveDown = false;
153.       
154.       
155.       println(moveStop);
156.     }
157.   
158.   if (key ==CODED){
159.         
160.   if (keyCode == UP){
161.     moveUp=true;
162.     //imgY++;
163.   }
164.   else if (keyCode == DOWN){
165.     moveDown=true;
166.     //imgY--;
167.   }
168.   else if (keyCode == LEFT){
169.     moveLeft=true;
170.     //imgX++;
171.   }
172.   else if (keyCode == RIGHT){
173.     moveRight=true;
174.     //imgX--;
175.   }
176.   }
177.   
178. }