UIImage Does Not Load Image

I am using UIImage to plot a png. I have getting a weird behavior that I cannot understand.

The following piece of code results in a nil im reference and thus prints "PROBLEM!"

UIImage *im = [[UIImage alloc] initWithContentsOfFile:@"tree.png"];开发者_JAVA技巧 

if (nil==im)
    NSLog(@"PROBLEM! IMAGE NOT LOADED\n");
else
    NSLog(@"OK - IMAGE LOADED\n");

This piece of code works finely:

UIImage *im = [UIImage alloc]; 

[im initWithContentsOfFile:@"tree.png"];

if (nil==im)
    NSLog(@"PROBLEM! IMAGE NOT LOADED\n");
else
    NSLog(@"OK - IMAGE LOADED\n");

What am I missing?

---

[[UIImage alloc] initWithContentsOfFile:@"tree.png"]; will return to you image if image /tree.png exist. But it doesn't exist. You should pass to initWithContentsOfFile full path, not only name of file.

Now, second one code works because of [UIImage alloc] return some reference that is not initialized. In next line your are trying to init it with [im initWithContentsOfFile:@"tree.png"]; but you've forgotten to save returned value in im, like this: im = [im initWithContentsOfFile:@"tree.png"];.

If image tree.png is saved in your bundle, then you can use such approach : UIImage *im = [UIImage imageNamed:@"tree.png"]; or such:

NSString *filePath = [[NSBundle mainBundle] pathForResource:@"tree" ofType:@"png"];
UIImage *im = [[UIImage alloc] initWithContentsOfFile:filePath]; 

---

Is the image in your bundle and is it a PNG image? The UIImage Documentation mentions the following when using initWithContentsOfFile:

An initialized UIImage object, or nil if the method could not find the file or initialize the image from its contents.

Also, since you are using the UIImage locally I assume from your code, you could just use the imageNamed: class method like so and it will search for the image in your main bundle:

UIImage *im = [UIImage imageNamed:@"tree.png"];

if (nil==im)
    NSLog(@"PROBLEM! IMAGE NOT LOADED\n");
else
    NSLog(@"OK - IMAGE LOADED\n");

---

try:

NSString *path = [[NSBundle mainBundle] pathForResource:@"tree" withExtension:@"png"];
UIImage *im = [[UIImage alloc] initWithContentsOfFile:path];

to load the image from your application bundle.

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BTW, your second piece of code is potentially dangerous. Actually initWithContentsOfFile: calls autorelease for the object, if file is not found. And if you tried to access image after a while, it would be an error (EXC_BAD_ACCESS).

So that you should always use init methods in pair with alloc and do not forget to release is somewhere.