# LZ4 Decompression (/libs/image_support/lz4)





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LVGL provides the extremely fast LZ4 decompression method found in the [LZ4
repository](https://github.com/lz4/lz4) on GitHub.  It can be used to reduce
binary image size.  The LZ4 compression is a lossless compression method.

The LVGL's built-in binary image decoder supports LZ4-compressed images.
The decoder supports both variable and file as image sources.  The original
binary data is directly decoded to RAM.

Which Library [#which-library]

If <ApiLink name="LV_USE_LZ4_INTERNAL" /> is enabled in `lv_conf.h`, LVGL's internal copy of the
LZ4 decompression algorithm is used (`./src/libs/lz4/lz4.c`).

If <ApiLink name="LV_USE_LZ4_EXTERNAL" /> is enabled, the LVGL project is assumed to be compiled and
linked with an external LZ4 library that provides the <ApiLink name="LZ4_decompress_safe" />
function.

One of them must be enabled to use LZ4 decompression.

Benefits [#benefits]

LZ4 is best at compressing data where compression and decompression speed is a
priority over compression ratio, making it ideal for applications like real-time data
processing.

<img alt="LZ4 compress statistics from lz4.org" src="__img0" />

Usage [#usage]

To use the LZ4 Decoder, enable it in `lv_conf.h` configuration file by setting
either <ApiLink name="LV_USE_LZ4_INTERNAL" /> or <ApiLink name="LV_USE_LZ4_EXTERNAL" /> to `1`.  LZ4 images can
then be used in the same way as other images.

```c title=" " lineNumbers=1
lv_image_set_src(img, "path/to/cogwheel.bin");
```

Generating LZ4 Compressed Binary Images [#generating-lz4-compressed-binary-images]

An LZ4 image binary can be directly generated from another image using script
`lvgl/scripts/LVGLImage.py`.

```bash title="bash" lineNumbers=1
./scripts/LVGLImage.py --ofmt BIN --cf I8 --compress LZ4 cogwheel.png
```

This will decompress `cogwheel.png`, and then re-compress it using LZ4 and write
the output to `./output/cogwheel.bin`.