[Bug]: Some WebP images do not display when opened from an SMB drive.

[bruhov]

Describe the bug

I am observing strange behavior when displaying WebP images from an SMB drive. Approximately 20% of all WebP images trigger an "Invalid File" error. One might assume the files are actually corrupt, but they open normally when copied to a local drive. Furthermore, regardless of their location, these files open correctly in Picasa Photo Viewer and the standard Windows image viewer (Microsoft Photos).

I have recorded a demonstration video and attached a sample of a file that causes this error.

The log entry reads as follows:
2026-07-14T23:13:05.316|Error|<no type>.<no method>|Failed to process WebP file at W:\smb\album-empty.webp

Steps to reproduce

1. Open the image locally – everything is fine.
2. Copy it to a network drive.
3. Open it from the network drive – "Invalid File" error.

Expected behavior

The image opens correctly from the network drive.

Actual behavior

output.mp4

Image format (if related to a specific file)

WebP

FlyPhotos version

2.7.0

Build source

GitHub MSI

Windows version

Windows 11 Pro 25H2 (build 26200.8655)

Architecture

x64

Additional context

No response

[brmarkus]

Does the network path contains cyrillic characters? Could that cause the problem? Could you try the path with "plain ASCII characters" for a quick smoke test?

[bruhov]

Does the network path contains cyrillic characters? Could that cause the problem? Could you try the path with "plain ASCII characters" for a quick smoke test?

Nope, just "W:\smb\album-empty.webp"

[brmarkus]

You mentioned Approximately 20% of all WebP images trigger an "Invalid File" error.

Could you share a file which can be opened successfully?

Your shared file looks like this using the tool MediaInfo:

General
Complete name                            : C:\Users\user\Desktop\621665621-a2788c0f-749d-4804-b840-1fc312f3dc0f.webp
Format                                   : WebP
File size                                : 1.29 KiB

Image
Format                                   : VP8
Width                                    : 450 pixels
Height                                   : 338 pixels
Color space                              : YUV
Bit depth                                : 8 bits
Compression mode                         : Lossy

Maybe VP8 codec, maybe YUV format?

[bruhov]

This image displays correctly. It is also VP8 and YUV.

General
Complete name                            : W:\smb\1.webp
Format                                   : WebP
File size                                : 29.6 KiB

Image
Format                                   : VP8
Width                                    : 550 pixels
Height                                   : 368 pixels
Color space                              : YUV
Bit depth                                : 8 bits
Compression mode                         : Lossy

[riyasy]

@bruhov @brmarkus
Fly had earlier faced some quirks while using Windows APIs related to network paths like in (#87)
Shall check.

[riyasy]

@bruhov , can you check if file attributes like "read-only", "hidden" etc are same for the success and failure files?

[bruhov]

There is no difference in attributes between the successful and failed files:

W:\smb>wmic datafile where name="W:\\smb\\good.webp" list /format:list

AccessMask=2032127
Archive=TRUE
Caption=W:\smb\good.webp
Compressed=FALSE
CompressionMethod=
CreationClassName=CIM_LogicalFile
CreationDate=20260715181246.582829+300
CSCreationClassName=Win32_ComputerSystem
CSName=DIMA-PC
Description=W:\smb\good.webp
Drive=w:
EightDotThreeFileName=w:\smb\good.webp
Encrypted=FALSE
EncryptionMethod=
Extension=webp
FileName=good
FileSize=30320
FileType=webp File
FSCreationClassName=Win32_FileSystem
FSName=NTFS
Hidden=FALSE
InstallDate=20260715181246.582829+300
InUseCount=
LastAccessed=20260715181246.582829+300
LastModified=20260715000755.067095+300
Manufacturer=
Name=W:\smb\good.webp
Path=\smb\
Readable=TRUE
Status=OK
System=FALSE
Version=
Writeable=TRUE

W:\smb>wmic datafile where name="W:\\smb\\bad.webp" list /format:list

AccessMask=2032127
Archive=TRUE
Caption=W:\smb\bad.webp
Compressed=FALSE
CompressionMethod=
CreationClassName=CIM_LogicalFile
CreationDate=20260714235351.798111+300
CSCreationClassName=Win32_ComputerSystem
CSName=DIMA-PC
Description=W:\smb\bad.webp
Drive=w:
EightDotThreeFileName=w:\smb\bad.webp
Encrypted=FALSE
EncryptionMethod=
Extension=webp
FileName=bad
FileSize=1326
FileType=webp File
FSCreationClassName=Win32_FileSystem
FSName=NTFS
Hidden=FALSE
InstallDate=20260714235351.798111+300
InUseCount=
LastAccessed=20260714235351.798111+300
LastModified=20260714231125.066816+300
Manufacturer=
Name=W:\smb\bad.webp
Path=\smb\
Readable=TRUE
Status=OK
System=FALSE
Version=
Writeable=TRUE

The webpinfo utility also detects no issues:

C:\Portable\libwebp-1.6.0-windows-x64\bin>webpinfo -summary "W:\\smb\\good.webp"

File: W:\\smb\\good.webp
RIFF HEADER:
  File size:  30320
Chunk VP8  at offset     12, length  30308
  Width: 550
  Height: 368
  Alpha: 0
  Animation: 0
  Format: Lossy (1)
Summary:
Number of frames: 1
Chunk type  :  VP8 VP8L VP8X ALPH ANIM ANMF(VP8 /VP8L/ALPH) ICCP EXIF  XMP
Chunk counts:    1    0    0    0    0    0    0    0    0     0    0    0
No error detected.

C:\Portable\libwebp-1.6.0-windows-x64\bin>webpinfo -summary "W:\\smb\\bad.webp"

File: W:\\smb\\bad.webp
RIFF HEADER:
  File size:   1326
Chunk VP8  at offset     12, length   1314
  Width: 450
  Height: 338
  Alpha: 0
  Animation: 0
  Format: Lossy (1)
Summary:
Number of frames: 1
Chunk type  :  VP8 VP8L VP8X ALPH ANIM ANMF(VP8 /VP8L/ALPH) ICCP EXIF  XMP
Chunk counts:    1    0    0    0    0    0    0    0    0     0    0    0
No error detected.

I noticed that FlyPicture successfully loads the file to generate a low-resolution preview but displays an error for the full-resolution image. I recorded a video showing me rapidly scrolling the mouse wheel back and forth to activate "Flying" mode.

FlyPhotos_mrV2X1GiCq.mp4

[riyasy]

Ok. I could successfully reproduce the issue in my PC. Shall check.

[riyasy]

Portable - https://github.com/riyasy/FlyPhotos/actions/runs/29470678280/artifacts/8364728339
Installer - https://github.com/riyasy/FlyPhotos/actions/runs/29470678280/artifacts/8364729186

Please check now.

[bruhov]

@riyasy All the images that weren't displaying before are now showing up correctly. Thanks!

I’ll add that, despite the commit message mentioning 16 KB, most of the non-working images were significantly larger, yet they are displaying properly now as well.