Questions on HW2-Spring07

Questions on HW2-Spring07

It is perfectly okay for your collage to have white space in it – lots of big blank areas. In fact, it's easiest if you are doing a mirrored composition. If you want to see examples of collages that are mirrored, check out some 1315 collages that use mirroring. Mark Guzdial

Question: Is there a limit to the size of our collage? - Student521

Officially no, but if it flows off the edges of the display then your TA may have a difficult time grading it. If your pictures are too big try playing around with the Picture scale(double factor) method to shrink them. -Joel Uthe

Question: I meant... can we make a small collage? But I realize now that's a stupid question... never mind! :) - Student521

Just don't use too many huge pictures or else they'll never load on the TAs' computers. You don't know how many students' homeworks actually crashed my computer last semester. -Dawn Finney

Question: Just out of curiosity, if you've dropped a picture into a world using a turtle, is there a way to pick the picture back up and make it disappear if you don't want it anymore?

I tried looking at the code and the javadocs, and I don't really see any way to do what you asked. I think in order to move that Picture you would need some reference to it, but I think it gets integrated into the World somehow (Might want to wait for a more definitive answer from Prof Guzdial). I don't |believe you're supposed to be making an animation though (so why not just delete that section of code?). -Dawn Finney

That's true; the question only came up because I was playing around with pictures and turtles in the interactions window. Thanks!

Question: The instructions say use FileChooser.getMediaPath() in the function...so what if we use a picture that isn't from the mediasources folder? would we have to send the picture in too along with the method?

Just for others with the same question. If you use a picture that is NOT from the Media Sources provided, then you must also submit that picture along with the rest of your homework -Dawn Finney

Question: Nevermind I got the answer from the instructions for that... but what does it mean turn in Picture.java if we added a new method to it? We can't add a new method to PictureCollage.java to alter the picture? or do we have to open up Picture.java to make a new method there?

Honestly it can be done either way in the Java world. For this assignment I would stick with putting any new Picture manipulation methods in Picture. PictureCollage should just have the main method. Of course this is how I would go about it ask your grading TA if you still have questions. As for submitting Picture.java again, we're afraid that you're going to use a new Picture method that you wrote for the last homework on this homework so we want you to submit your Picture.java if you do end up using your own methods. -Dawn Finney

Question: Do we have to use compose to create our collage or can we just use turtles. Also while creating our collage can we use two different images that are already flipped or do we have to flip the same image?

"You must use a Turtle to do some of your drawing!!" Exact quote from the homework description meaning yes you can use compose but you must also use a Turtle. At the very least you need to have a Turtle. As for the second part, "you need to have one picture appear four times: The original time, then three other times with some image manipulation. You're welcome to add additional pictures if you'd like. The whole collage should be mirrored in some direction." As long as you follow the parameters specified in the homework description ie have that one picture that appears 4 times and the whole collage must be mirrored in some direction, you're welcome to have more pictures and flip the ones you want. You have to use Java to do the flipping no cheating with Paint or Photoshop, etc. -Dawn Finney

Question: Is there anything specific you'd like us to include in the comments (i.e. the entire path when we use getMediaPath)? DrJava is not allowing me to set my media path to a different folder, how do I get around this?

No, the entire path from getMediaPath() is not necessary. Comments should definitely include your first and last name, your Prism ID (gtg, gth, or that new thing), and if you don't use your Prism email account, an email account where you can easily be reached (in case you forgot to attach a file, etc). Your comments should basically describe what is happening in your code or what you want to happen. Comments help you and the TAs understand what you are doing. Comments can also help a TA award partial credit in case your code fails but your logic (as described in the comments) is correct. You're probably going to have to post what you're inputting into Dr. Java for the second question. I'd check out one of the similar questions below. Post again if that one doesn't answer your question. -Dawn Finney

Question: When you say that we can't use any of the mirror methods in the Picture class does that mean in order to mirror we either have to write our own mirror method or use turtles?

Whichever one is easier. I'd suggest using turtles. Remember that when a turtle drops a Picture, it always drops on the turtle's right foot...so what happens when you change the turtle's heading (ie turn()) and then drop the Picture...? :) -Dawn Finney

Wow thanks a lot that explanation makes a hell of a lot of sense! This assignment has gotten a bit easier sounding.

Question:

FileChooser.setMediaPath("D:/cs1316/mediasources/")

This line won't work when typed in. This is my working directory as of right now:Welcome to DrJava. Working directory is C:\Documents and Settings\Najma Shaikh\Desktop\cs1316\java-source This is the error I get: Couldn't load the file D:/cs1316/mediasources/swan.jpg However, this file was in the folder. Could you please provide me some feedback as to why this line doesn't work and what I can do about it.Thanks for your help.

Try doing FileChooser.setMediaPath("C:/Documents and Settings/Najma Shaikh/Desktop/cs1316/mediasources/"); I'm assuming your mediasources folder is in the same directory as your java-source folder. FileChooser.setMediaPath() basically takes in a path to a folder as a String and saves it. When you call FileChooser.getMediaPath(someString), it gets that path and appends someString on the end to create a complete path to something (ie. .jpg, .midi). All this is to make your life easier so you don't have to type every path out and also makes it easier for TAs to grade your homework. Please DO NOT include FileChooser.setMediaPath() in your homework assignment! It only needs to be done ONCE on YOUR computer (do it in the Interactions Pane). Including FileChooser.setMediaPath() in your homework just messes up the TA's media path and believe me it makes TAs very angry. -Dawn Finney

Question: I don't see a PictureCollage.java. I see a MyCollage.java though. What should I use?

Create a PictureCollage.java. Sounds simple enough, no? Feel free to use MyCollage.java as a guide though there might be some better files to look at out there. -Dawn Finney

ah...ok thanks.

Question: I am trying to use the library computers for this homework and they do not have Dr. Java. They have JGrasp and JCreator. Which one of these should I use or should I just try to download Dr. Java here?

You can use either one (or download Dr. Java. Can you download Dr. Java on a library machine?). You can use any IDE you want to program in. It's just in this class we will focus Dr. Java and will be less likely to be able to help you if you use something other than Dr. Java. -Dawn Finney

Question: I've written the code for my collage, and when typed into the interactions pane step by step, produces a picture. However, when I try to compile the full document, I get a lot of errors in the middle of the code (primarily dealing with .compose, however the exact same code copied into interactions works fine). Whats going on?

I've noticed that Dr. Java's interactions pane will ignore certain syntax errors that the Java compiler freaks out about. I'd have to see a sample of a line with an error and the error message to tell you more. -Dawn Finney

Question: Can we do everything with compose and then just have a random turtle to fulfull the requirement? Or do we have to use Turtles to do the symmetry part?

You can just have the random little Turtle, but he's got to do something with the pictures not necessarily the symmetry part. -Dawn Finney

Question: umm...I tried to do FileChooser.setMediaPath() in the interactions pane to set the path but I get: Error: No 'setMediaPath' method in 'FileChooser' with arguments: ()

You have to give it a path to your media sources folder. Like mine is C:/Program Files/cs1316/MediaSources/ so I would put FileChooser.setMediaPath("C:/Program Files/cs1316/MediaSources/"); in the interactions pane. -Dawn Finney

Question: Do all 4 pictures need to have some different image manipulation? Or can we just have 2 types of image manipulation?

"You need to have one picture appear four times: The original time, then three other times with some image manipulation. You're welcome to add additional pictures if you'd like," from Homework Description -Dawn Finney

Question: What else is there that the Turtles can do, if they don't do the symmetry?

No earthly clue. Drop one picture? It's so much easier just to let the Turtles to do the symmetry. -Dawn Finney

Question: How do we actually go about testing one of the methods? Say Markscollage.java. What do we type in the interactions pane?

If it's the main method you want to run. Click compile and then type
```
java Markscollage
```
in the Interactions Pane. Or you can compile and then click the Run button somewhere in the upper right in Dr. Java. -Dawn Finney

Question: When I try to compile this project, I get the error: File: (no associated file) [line: (no source location)] Error: java.lang.NoSuchMethodError: com.sun.tools.javac.util.Options.put(Ljava/lang/String;Ljava/lang/String;)

I've never seen that error before...Did you save? Uh feel free to email me your homework and I'll take a look at it. -Dawn Finney

Question: So if we make a turtle turn 180 degrees and let it drop a picture will the picture be upside down as opposed to if the turtle drops a picture while its facing up?

Do you really want me to answer this or do you want to try it out and see for yourself? -Dawn Finney

good point.

Question: Does "some sort of image manipulation" mean we have to have some sort of if/then or iteration in our code because I first did mine with a while loop, but it took a long time to load so I got rid of all my iterations and just wrote them out.

No. It means that you do something like myPic.increaseRed() and then drop it. No loops or if/else needed. -Dawn Finney

Not a Question: Dawn's answers humor me. Student521

Glad to be of service. :) -Dawn Finney

Another Question!: I am getting a weird error

Error: C:\Documents and Settings\Richard\My Documents\School Work\Spring07\CS1316\Applications\java-source-Fall06\java-source-Fall06\RicPic.java:4: identifier expected

This happens 23 times in the same compile on different lines. Please help!

Is your code actually within the curly brackets of the main method? Sounds like it isn't. Otherwise post again. I, however, I am going to bed and will answer more questions in the morning. -Dawn Finney
It also sounds possible that you haven't identified the type of your variable. Remember unlike some other programming languages, in java you have to specifically say what type of variable you want. int myVar = 1; Turtle fred = new Turtle(w); Picture p = new Picture(FileChooser.getMediaPath("swan.jpg"); etc. -Joel Uthe

Dawn ROCKS! –Mark Guzdial

Woot. -Dawn Finney

Question: I uploaded my final collage to the HW2 Gallery...would this count as the entire canvas being mirrored? or should i make it so there are 8 pictures total? Student521

Here are some examples of pictures that use mirroring. I don't think yours quite fits the definition of mirroring. It needs to be symmetric horizontally or vertically.

Horizontal

Vertical

Taken from the website. In no way do I claim these to be my creations. -Dawn Finney

Question: The picture I'd like to use is a .gif file – the methods of the Picture class don't seem to have the same effect on .gif files as they do .jpg files. Is it because the two files types are encoded differently? Are we allowed to submit .gif files?

The two files are encoded differently (how they're different I don't exactly know). If you can get the .gif to work properly (you can manipulate it using Picture methods and play with them using Turtles) I don't see why you couldn't submit a .gif file. In fact I just tested it out and it seems to work okay. I'd check with your grading TA if you still have questions. -Dawn Finney

Question: Does our collage have to be centered on the canvas?? What would be a good way (besides hard keying the dimensions) to center the collage on the canvas?

If the thing you're drawing on is called "canvas" and it's a Picture then you can use canvas.getHeight() to get the height of the Picture and canvas.getWidth() to get the width of the Picture (Don't know you if you can do it with a World too. I would have to try it out). The rest is simple mathematics. -Dawn Finney

Question: How do we use a function like negate() if it is void in picture.java? Should we write the code for it in the collage area?

Just do something like
```
Picture p = new Picture(FileChooser.getMediaPath("swan.jpg"));
p.negate();
Turtle mike = new Turtle(new World());
mike.drop(p);
```
in PictureCollage.java. A void function just doesn't return anything. It doesn't mean you can't use or something. No don't rewrite it. -Dawn Finney

Question: Is it necessary to pull the pen up on the turtle or is it ok with the lines?

uh if your turtle is named bob then bob.penUp(); should pull the pen up. I don't know if it's required or not. -Dawn Finney

Question: What exactly will the T.A.'s type into the command line to test our programs?

For this one, the TAs will just compile and run PictureCollage.java's main method. So compile and then
```
java PictureCollage
```
in the interactions pane. -Dawn Finney

Question: I'm confused as to, are we supposed to have 4 pics total on our hw2 or 8 pics total? It seems like you mean 4: "You need to have one picture appear four times: The original time, then three other times with some image manipulation". But maybe its 8 total with the symmetry.

I've been wondering about the above question too...that's the sole thing that's kept me from turning this assignment in already.

No clue. I would ask your grading TA or REMOVEDel. I personally would accept the 4 picture one, but I'm not exactly grading anything. Just to be safe, you could do the 8 picture one. That one is definitely acceptable. -Dawn Finney

Dawn ur awesome. marry me! haha.

Well I'm entertained. :) -Dawn Finney

Dawn's bringing sexy back... YEAHHH!

If I have time, maybe. -Dawn Finney

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Homeworks-Spring 2007 last edited on 19 April 2007 at 10:45 pm by c-76-17-114-206.hsd1.ga.comcast.net