Question: Best way to load and save files from a buffer when file type is not known

I’m loading images from the IFormFile container. I’m not sure what the best way is to find the image type so that I can save the images in the original format they were uploaded in. IFormFile.ContentType might not be reliable. I’m aware that libvips sniffs the first few bytes when loading a file from disk, is there a way to replicate that behaviour in this library? Perhaps to sniff from the intermediary buffer I’m using to load the image.

[kleisauke]

libvips has two useful functions to quickly identify the image type:

• vips_foreign_find_load
• vips_foreign_find_load_buffer

I just made these functions available in NetVips with commit https://github.com/kleisauke/net-vips/commit/3fffefc9c2aab64fbc3928d629823595ab333335.

Note that these functions will not detect truncated images, it just performs some basic verification of image metadata. For example, reading a buffer with GIF89a will result in VipsForeignLoadGifBuffer.

If you also want to detect broken images, you can use this: https://github.com/kleisauke/net-vips/blob/3fffefc9c2aab64fbc3928d629823595ab333335/samples/NetVips.Samples/Samples/IdentifyExtension.cs#L40-L63

[kleisauke]

NetVips 1.1.0-rc3 is released on NuGet. If there’s nothing reported for a week, this will become 1.1.0 final.