An Image file, or "source image", stores a single 2D image, typically in RGB format with an optional Alpha (opacity) channel. This is not the same as a texture file used for 3D rendering, but an image file may be referenced as a source image by a texture.txt file.
A number of standard interchange formats are support by Trainz for image files. In some cases, limitations may be set on what features may be used in the image file- for example, specific types of compression or format options.
Please be aware of the filename character restrictions when naming texture and image files.
Supported File Formats
PNG is a lossless compressed image format with alpha channel support. This is the best choice where compatibility with older versions of Trainz is not required.
Targa is a lossless image format with optional compression and optional alpha channel. This is a sensible choice for texture source images where compatibility with older versions of Trainz is desired.
JPEG is a lossy image compression format with no alpha channel support. This is suitable for larger non-texture images, such as thumbnails, screenshots, etc. This format should generally be avoided for textures since it will typically lead to the image being compressed in a lossy format (JPG), decompressed, and finally recompressed again into another lossy format.
Since each open-edit-save cycle may further degrade the quality of a JPEG file, it is not recommended to store work-in-progress images in this format.
Use in Texture Files
Image files may be used as the source image for texture files to be used in 3D rendering. Additional restrictions and options are present for images used as a texture; the texture file page should be consulted for details.
A single image file should not be simultaneously used as both a source image for a texture file and also for other purposes. When archiving content for distribution, N3V Games may perform a one-way conversion of all texture files into a device-specific format, erasing any source images used by the texture. In this scenario, the source image is no longer available for other uses.
Images should use the sRGB color space except where documentation for the specific use-case indicates otherwise.