mirror of https://github.com/arendst/Tasmota.git
51 lines
2.0 KiB
Markdown
51 lines
2.0 KiB
Markdown
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# PNG decoder for LVGL
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Allow the use of PNG images in LVGL. This implementation uses [lodepng](https://github.com/lvandeve/lodepng) library.
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## Get started
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- Download or clone this repository
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- [Download from GitHub](https://github.com/littlevgl/lv_lib_lodepng/archive/master.zip)
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- Clone: `git clone https://github.com/littlevgl/lv_lib_png.git`
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- Include the library: `#include "lv_lib_png/lv_png.h"`
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- Initalize the decocer with `lv_png_init()`
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- Test with the following code:
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```c
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LV_IMG_DECLARE(png_decoder_test);
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lv_obj_t * img = lv_img_create(lv_scr_act(), NULL);
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lv_img_set_src(img, &png_decoder_test);
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```
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## Use PNG images from file
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By deafult `lodepng` uses C file IO API (e.g. `fopen`) and images can be opened like this:
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```c
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lv_img_set_src(img, "./lv_lib_lodepng/png_decoder_test.png");
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```
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If you want to make `lodepng` to use LVGL's file system API add `#define LV_PNG_USE_LV_FILESYSTEM 1` to the end of your`lv_conf.h`.
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In this case you need to [register a driver](https://docs.lvgl.io/latest/en/html/overview/file-system.html) fo LVGL. The following functions are required:
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- `open_cb()`
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- `read_cb()`
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- `close_cb()`
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- `size_cb()`
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After that fiels can be opened like this:
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```c
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lv_img_set_src(img, "P:lv_lib_lodepng/png_decoder_test.png");
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```
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Note that the path of the file might be different.
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## Use PNG images from flash
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To store a PNG image in flash it needs to be converted to C array with [Online Image converter](https://lvgl.io/tools/imageconverter). Choose `Raw with alpha` Color format and `C array` Output format. Copy the result C array to your project and use it like this:
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```c
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LV_IMG_DECLARE(my_test_img);
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lv_obj_t * img = lv_img_create(lv_scr_act(), NULL);
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lv_img_set_src(img, &my_test_img);
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```
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## Learn more
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To learn more about the PNG decoder itself read [this blog post](https://blog.littlevgl.com/2018-10-05/png_converter)
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To learn more about the Image decoder interface of LittlevGL read the realevant part of the [documentation](https://docs.littlevgl.com/en/html/overview/image.html#image-decoder).
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