# Guidelines for Images

Not all images are suitable for tracking. For best results, pick images that are distinct, asymmetric, detailed and that have little or no text.

## Distinct

A distinct image has distinguishable areas - quite unlike a repetitive pattern!

| Suitable :heavy_check_mark: | Unsuitable :x: |
| --------------------------- | -------------- |
| [![](./img/guidelines-for-images-10.jpg "Based on https://pixabay.com/pt/illustrations/unic%c3%b3rnio-gal%c3%a1xia-fantasia-estrela-3115021/ (Tarishart)")](./img/guidelines-for-images-10.jpg){ ._blank } | [![](./img/guidelines-for-images-1.jpg "Source: https://www.pexels.com/pt-br/foto/papel-de-parede-abstrato-roxo-e-azul-430207/ (Scott Webb)")](./img/guidelines-for-images-1.jpg){ ._blank } |
| [![](./img/guidelines-for-images-9.jpg "Based on https://pixabay.com/pt/illustrations/o-macaco-chimpanz%c3%a9-macaco-banana-4701265/ (Dmitry Abramov) and https://pixabay.com/pt/vectors/panorama-crep%c3%basculo-luz-noite-c%c3%a9u-1844227/ (Wild0ne)")](./img/guidelines-for-images-9.jpg){ ._blank } | [![](./img/guidelines-for-images-4.jpg "Source: https://www.pexels.com/pt-br/foto/imagem-completa-da-estrutura-arquitetonica-248921/ (Pixabay)")](./img/guidelines-for-images-4.jpg){ ._blank } |

## Asymmetric

Asymmetric images help the engine determine their orientation. When evaluating symmetry, you must not take colors into account.

| Suitable :heavy_check_mark: | Unsuitable :x: |
| --------------------------- | -------------- |
| [![](./img/guidelines-for-images-12.jpg "Source: https://www.pexels.com/pt-br/foto/gatinho-branco-e-cinza-cheirando-flor-da-margarida-branca-1472999/ (Alex Bargain)")](./img/guidelines-for-images-12.jpg){ ._blank } | [![](./img/guidelines-for-images-2.jpg "Source: https://www.pexels.com/pt-br/foto/frutas-citricas-brancas-vermelhas-e-amarelas-1415734/ (Aleksandar Pasaric)")](./img/guidelines-for-images-2.jpg){ ._blank } |
| [![](./img/guidelines-for-images-11.jpg "Based on https://pixabay.com/pt/photos/sof%c3%a1-surreal-olhos-cachorro-arte-749629/ (0fjd125gk87)")](./img/guidelines-for-images-11.jpg){ ._blank } | [![](./img/guidelines-for-images-5.jpg "Source: https://www.pexels.com/pt-br/foto/lapis-de-cor-amarelo-e-azul-1762851/ (Ann H)")](./img/guidelines-for-images-5.jpg){ ._blank } |

## Detailed

A detailed image has lots of different details with sufficient contrast. There isn't much blank space!

| Suitable :heavy_check_mark: | Unsuitable :x: |
| --------------------------- | -------------- |
| [![](./img/guidelines-for-images-3.jpg "Source: https://www.pexels.com/pt-br/foto/borboleta-flor-broto-flora-5647855/ (Ольга Бочкарева)")](./img/guidelines-for-images-3.jpg){ ._blank } | [![](./img/guidelines-for-images-7.jpg "Source: https://www.pexels.com/pt-br/foto/6985119/ (Gradienta)")](./img/guidelines-for-images-7.jpg){ ._blank } |
| [![](./img/guidelines-for-images-8.jpg "Source: https://www.pexels.com/pt-br/foto/fotografia-de-close-up-de-arara-azul-e-amarela-1453550/ (Susanne Jutzeler)")](./img/guidelines-for-images-8.jpg){ ._blank } | [![](./img/guidelines-for-images-6.jpg "Source: https://unsplash.com/photos/KF-r4-KM9pM (Gian Gomez)")](./img/guidelines-for-images-6.jpg){ ._blank } |

## Little or no text

It follows from the other recommendations that images with too much text - particularly small text - are unsuitable for tracking. Feature points will tend to cluster around the letters and will not be distinct enough. A little bit of text is okay.

| Suitable :heavy_check_mark: | Unsuitable :x: |
| --------------------------- | -------------- |
| [![](./img/guidelines-for-images-14.jpg "Based on https://pixabay.com/pt/vectors/bruxa-vassoura-gato-chap%c3%a9u-magia-5635225/ (ArtRose)")](./img/guidelines-for-images-14.jpg){ ._blank } | [![](./img/guidelines-for-images-13.jpg "Based on https://pixabay.com/pt/vectors/bruxa-vassoura-gato-chap%c3%a9u-magia-5635225/ (ArtRose)")](./img/guidelines-for-images-13.jpg){ ._blank } |
| [![](./img/guidelines-for-images-16.jpg "Based on https://pixabay.com/pt/vectors/bruxa-vassoura-gato-chap%c3%a9u-magia-5635225/ (ArtRose)")](./img/guidelines-for-images-16.jpg){ ._blank } | [![](./img/guidelines-for-images-15.png "Based on https://pixabay.com/pt/vectors/bruxa-vassoura-gato-chap%c3%a9u-magia-5635225/ (ArtRose)")](./img/guidelines-for-images-15.png){ ._blank } |

## Other considerations

### Aspect ratio

Prefer images whose aspect ratio (the ratio _width ÷ height_) is somewhere between the aspect ratio of the target device (16:9 is a common aspect ratio) and 1:1 (a square). It's okay to use landscape or portrait mode - the engine will make the necessary adjustments.

### Resolution

Using a Ultra HD image is of no benefit, because the engine will downscale it. A tiny image isn't desirable either, because some details may be lost and the engine will likely have to upscale it. Use an image that has its details preserved. It's even better if that image can be loaded quickly!

### Physical materials

When printing your images, keep the following in mind:

- Prefer non-reflective materials. Avoid shiny materials such as glossy paper. Reflections may generate artifacts in the video and interfere with the tracking.
- Materials should be rigid. Don't use something that can be distorted too easily.
- Use quality materials.

### Brightness on screens

If you're using a screen to display your images, make sure to adjust its brightness. If the screen is too bright (too dark), it will cause overexposure (underexposure) in the video and tracking difficulties - details of the images will be lost. Screen reflections are also undesirable.

### Test it!

In addition to the guidelines presented above, you should always experiment with your images and make sure it all works as intended. Keep in mind that proper lighting of the physical environment is also very important!

See also: [Recommendations for WebAR](./recommendations.md).