How to read embedded png texture in FBX? (iOS/macOS)

[dmsurti]

I am trying to read an embedded texture (png) in an FBX file. While I can correctly detect an embedded texture; I am not able to read texture->pcData. The relevant ObjC code:

               DLog(@" This is an embedded texture ");
               embeddedTexture = true;
                if(![[texFileName substringWithRange:NSMakeRange(0, 1)] isEqualToString:@"*"]) {
                    return;
                }
               int k = [texFileName substringFromIndex:1].intValue;
               const struct aiTexture *texture = aiScene->mTextures[k];
                NSData *imageData = [NSData dataWithBytes:&texture->pcData length:texture->mWidth];
                
                uint8_t c;
                [imageData getBytes:&c length:1];
                
                switch ((c)) {
                    case 0x89:
                        DLog(@" This is a PNG");
                        break;
                        
                    default:
                        DLog(@" This is not a PNG");
                        break;
                }

When I run the above code, the output on console is:

2017-08-30 13:40:16.867287+0530 OSX-Example[7674:196288] -[AssimpImporter makeMaterialPropertyForMaterial:inScene:withTextureType:withSCNMaterial:atPath:] [Line 599]  has 1 textures
2017-08-30 13:40:16.867356+0530 OSX-Example[7674:196288] -[AssimpImporter makeMaterialPropertyForMaterial:inScene:withTextureType:withSCNMaterial:atPath:] [Line 612]  This is an embedded texture
2017-08-30 13:40:16.868097+0530 OSX-Example[7674:196288] -[AssimpImporter makeMaterialPropertyForMaterial:inScene:withTextureType:withSCNMaterial:atPath:] [Line 630]  This is not a PNG

As can be seen, the code detects from the raw data first byte, that it is not a PNG.

Is it me that is doing something wrong (hopefully, so :-) ? From the output however it seems the pcData is incorrect.

Is there any importer runtime setting or a build setting to ensure that pcData is populated correctly?

My system specs:

macOS: 10.12
Assimp lib: v4.0.1

[dmsurti]

@kimkulling With the following changes in fbx loader related code:

1. adding a uint_8 to hold raw image data in texture.h:

    uint8_t *rawImageData;

2. Then reinterpret the pcData in FBXConverter.cpp as such:

   // steal the data from the Video to avoid an additional copy
    out_tex->pcData = reinterpret_cast<aiTexel*>( const_cast<Video&>( video ).RelinquishContent() );
    out_tex->rawImageData = reinterpret_cast< uint8_t *>(out_tex->pcData);

fixes the above problem. Without reinterpreting the pcData, in iOS/macOS I get invalid memory address for the memory buffer.

While this fix works, how correct/valid is it? I don't have FBX internals or Assimp internals knowledge in depth to judge; if you think this is valid, I could send a Pull Request with the fix.

---

With the above fix, generating an image object requires only the following:

    const struct aiTexture *aiTexture = aiScene->mTextures[index];
    NSData *imageData = [NSData dataWithBytes:aiTexture->pcData
                                       length:aiTexture->mWidth];
    self.imageDataProvider =
        CGDataProviderCreateWithCFData((CFDataRef)imageData);
    NSString* format = [NSString stringWithUTF8String:aiTexture->achFormatHint];
    if([format isEqualToString:@"png"]) {
        DLog(@" Created png embedded texture ");
        self.image = CGImageCreateWithPNGDataProvider(
            self.imageDataProvider, NULL, true, kCGRenderingIntentDefault);
    }
    if([format isEqualToString:@"jpg"]) {
        DLog(@" Created jpg embedded texture");
        self.image = CGImageCreateWithJPEGDataProvider(
            self.imageDataProvider, NULL, true, kCGRenderingIntentDefault);
    }

[kimkulling]

There was a bug in the embeddded texture lookup, check: #1620