Why the use of cvLoadImage of OpenCV always return NULL on IOS?

Question

I write some code to run on the iPad, I use cvLoadImage() to read image from Bundle Resources, but it always return NULL, I don't know why?

i add image to Bundle Resources,i think it does't need path,i just write the image's name. it's like "cvLoadImage("lena.jpg");" — Ello, Sep 14 '12 at 09:01
You shouldn't make assumptions about the current working directory. Get the path to the bundle first and prefix your filename with the path. — Paul R, Sep 14 '12 at 10:28

score 4 · Accepted Answer · edited May 23 '17 at 12:23

4

You can't load an image from your app bundle directly into OpenCV … Getting a proper cv::Mat involves two steps:

1.) Load your image using UIImage
2.) Convert the UIImage to a cv::Mat

Which looks like this:

cv::Mat img = [UIImageCVMatConverter cvMatFromUIImage:[UIImage imageNamed:@"my_image.png"]];

Grab the UIImageCVMatConverter class from this thread: OpenCV install in xcode

Hope that helps!

edited May 23 '17 at 12:23

Community

answered Sep 15 '12 at 10:10

dom

In fact,I use another way to load image,but your answer is right,too – Ello Oct 26 '12 at 00:54
Please, can you explain why the images in the bundle can't be loaded directly with opencv functions? – Joe Aspara Sep 26 '15 at 15:33

score 0 · Answer 2 · answered Sep 14 '12 at 09:07

0

use directly

[UIImage imageWithNamed:@"photo.png"];

if the image is in Bundle you can use directly.

answered Sep 14 '12 at 09:07

Sanoj Kashyap

but i need to processing this image with the method of OpenCV – Ello Sep 14 '12 at 09:11

2 Answers2