If the image is too big, the program crashes when imread, if I want to throw an error when the image can’t be loaded, let the program continue to run, if I don’t want to use exception capture, then is there a good way to deal with it?
You need to use some library or external program to read the image’s dimensions without actually loading it.
If the dimensions are too big, skip that image. This is just general programming, not an OpenCV problem.
OpenCV has some env vars to limit how large an image will be loaded.
all of them, specifically imgcodecs-related ones:
https://docs.opencv.org/4.x/d6/dea/tutorial_env_reference.html#autotoc_md990
here’s an excerpt. pick what looks good to you.
| name | type | default | description |
|---|---|---|---|
| OPENCV_IMGCODECS_AVIF_MAX_FILE_SIZE | num | 64MB | limit input AVIF size |
| OPENCV_IMGCODECS_WEBP_MAX_FILE_SIZE | num | 64MB | limit input WEBM size |
| OPENCV_IO_MAX_IMAGE_PARAMS | num | 50 | limit maximum allowed number of parameters in imwrite and imencode |
| OPENCV_IO_MAX_IMAGE_WIDTH | num | 1 << 20, limit input image size to avoid large memory allocations | |
| OPENCV_IO_MAX_IMAGE_HEIGHT | num | 1 << 20 | |
| OPENCV_IO_MAX_IMAGE_PIXELS | num | 1 << 30 | |
| OPENCV_IO_ENABLE_OPENEXR | bool | true (set build option OPENCV_IO_FORCE_OPENEXR or use external OpenEXR), false (otherwise) | enable OpenEXR backend |
| OPENCV_IO_ENABLE_JASPER | bool | true (set build option OPENCV_IO_FORCE_JASPER), false (otherwise) | enable Jasper backend |
Because I don’t want to use some other libraries to process this image, if you can’t handle too large a picture when imread in OpenCV, why not return a null value, but let the program just crash? I don’t really understand this design idea.
I feel that environmental variables are a palliative solution, and there is a better way to deal with it. I feel that environmental variables are a palliative solution, and there are better ones
you could always submit an issue on different handling of large images.
you know you can set env vars from inside your program, right?
if you don’t want to use the facilities that OpenCV offers, you’ll have to use image loading libraries directly, instead of through OpenCV’s abstraction.
if you don’t want to use such libraries either, you are out of options.
there is nothing more we can do for you. good luck.
Thank you very much for your answer
ah, cmon, it’s just fopen() / fseek() to find out how many bytes there are on disk. built into the language since like 1970 !
(really, general progging skills, do you have any ??)
then, just skip any file > 10mb, done.
a decent heuristic but nothing prevents one from crafting large images that compress well.