377cc5aa80
Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com> Co-authored-by: Liam Howatt <30486941+liamHowatt@users.noreply.github.com>
69 lines
1.7 KiB
ReStructuredText
69 lines
1.7 KiB
ReStructuredText
.. _lodepng_rst:
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===============
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LodePNG Decoder
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===============
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**LodePNG** is an LVGL interface to the LodePNG library --- a PNG encoder and decoder
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in C and C++, without any dependencies, giving you an alternate way to use PNG images
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in your LVGL UI.
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For a detailed introduction, see: https://github.com/lvandeve/lodepng .
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If enabled in ``lv_conf.h`` by setting :c:macro:`LV_USE_LODEPNG` to ``1``, LVGL will
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register a new image decoder automatically so PNG files can be used directly as an
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image source.
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.. note::
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A file system driver needs to be registered to open images from files. To do so,
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follow the instructions in :ref:`file_system`.
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.. |times| unicode:: U+000D7 .. MULTIPLICATION SIGN
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The whole PNG image is decoded, so
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width |times| height |times| 4
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bytes of RAM is required from the LVGL heap. The decoded image is stored in RGBA
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pixel format.
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Since it might take significant time to decode PNG images LVGL's
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:ref:`overview_image_caching` feature can be useful.
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Compressing PNG Files
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*********************
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PNG file format supports True color (24/32 bit), and 8-bit palette colors.
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Usually cliparts, drawings, icons and simple graphics are stored in PNG format,
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that do not use the whole color space, so it is possible to compress further
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the image by using 8-bit palette colors, instead of 24/32 bit True color format.
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Because embedded devices have limited (flash) storage, it is recommended
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to compress images.
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One option is to use a free online PNG compressor site,
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for example Compress PNG: https://compresspng.com/
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.. _lodepng_example:
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Example
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*******
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.. include:: ../../examples/libs/lodepng/index.rst
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.. _lodepng_api:
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API
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***
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:ref:`lodepng_h`
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:ref:`lv_lodepng_h`
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