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== Example == | == Example == | ||
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=== Load an SJPG image === | === Load an SJPG image === | ||
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2022年6月28日 (火) 13:00時点における版
https://docs.lvgl.io/8.2/libs/sjpg.html
英文 | 自動翻訳 |
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JPG decoder
Allow the use of JPG images in LVGL. Besides that it also allows the use of a custom format, called Split JPG (SJPG), which can be decoded in more optimal way on embedded systems.
Overview
- Supports both normal JPG and the custom SJPG formats.
- Decoding normal JPG consumes RAM with the size fo the whole uncompressed image (recommended only for devices with more RAM)
- SJPG is a custom format based on "normal" JPG and specially made for LVGL.
- SJPG is 'split-jpeg' which is a bundle of small jpeg fragments with an sjpg header.
- SJPG size will be almost comparable to the jpg file or might be a slightly larger.
- File read from file and c-array are implemented.
- SJPEG frame fragment cache enables fast fetching of lines if available in cache.
- By default the sjpg image cache will be image width * 2 * 16 bytes (can be modified)
- Currently only 16 bit image format is supported (TODO)
- Only the required partion of the JPG and SJPG images are decoded, therefore they can't be zoomed or rotated.
Usage
If enabled in lv_conf.h
by LV_USE_SJPG
LVGL will register a new image decoder automatically so JPG and SJPG files can be directly used as image sources. For example:
lv_img_set_src(my_img, "S:path/to/picture.jpg");
Note that, a file system driver needs to registered to open images from files. Read more about it here or just enable one in lv_conf.h
with LV_USE_FS_...
Converter
Converting JPG to C array
- Use lvgl online tool https://lvgl.io/tools/imageconverter
- Color format = RAW, output format = C Array
Converting JPG to SJPG
python3 and the PIL library required. (PIL can be installed with pip3 install pillow
)
To create SJPG from JPG:
- Copy the image to convert into
lvgl/scripts
cd lvgl/scripts
python3 jpg_to_sjpg.py image_to_convert.jpg
. It creates both a C files and an SJPG image.
The expected result is:
Conversion started... Input: image_to_convert.jpg RES = 640 x 480 Output: Time taken = 1.66 sec bin size = 77.1 KB walpaper.sjpg (bin file) walpaper.c (c array) All good!
Example
Load an SJPG image
API
Functions
- void lv_split_jpeg_init(void)