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managed_components/espressif__esp_jpeg/README.md

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+# JPEG Decoder: TJpgDec - Tiny JPEG Decompressor
+
+[![Component Registry](https://components.espressif.com/components/espressif/esp_jpeg/badge.svg)](https://components.espressif.com/components/espressif/esp_jpeg)
+![maintenance-status](https://img.shields.io/badge/maintenance-actively--developed-brightgreen.svg)
+
+TJpgDec is a lightweight JPEG image decompressor optimized for embedded systems with minimal memory consumption.
+
+On some microcontrollers, TJpgDec is available in ROM and will be used by default, though this can be disabled in menuconfig if desired[^1].
+
+[^1]: **_NOTE:_** When the ROM decoder is used, the configuration can't be changed. The configuration is fixed.
+
+## Features
+
+**Compilation configuration:**
+- Stream input buffer size (default: 512 bytes)
+- Output pixel format (default: RGB888; options: RGB888/RGB565)
+- Enable/disable output descaling (default: enabled)
+- Use table-based saturation for arithmetic operations (default: enabled)
+- Use default Huffman tables: Useful from decoding frames from cameras, that do not provide Huffman tables (default: disabled to save ROM)
+- Three optimization levels (default: 32-bit MCUs) for different CPU types:
+  - 8/16-bit MCUs
+  - 32-bit MCUs
+  - Table-based Huffman decoding
+
+**Runtime configuration:**
+- Pixel format options: RGB888, RGB565
+- Selectable scaling ratios: 1/1, 1/2, 1/4, or 1/8 (chosen at decompression)
+- Option to swap the first and last bytes of color values
+
+## TJpgDec in ROM
+
+On certain microcontrollers, TJpgDec is available in ROM and used by default. This can be disabled in menuconfig if you prefer to use the library code provided in this component.
+
+### List of MCUs, which have TJpgDec in ROM
+- ESP32
+- ESP32-S3
+- ESP32-C3
+- ESP32-C6
+- ESP32-C5
+- ESP32-C61
+
+### Fixed compilation configuration of the ROM code
+The ROM version uses the following fixed settings:
+- Stream input buffer: 512 bytes
+- Output pixel format: RGB888
+- Output descaling: enabled
+- Saturation table: enabled
+- Optimization level: Basic (JD_FASTDECODE = 0)
+
+### Pros and cons using ROM code
+
+**Advantages:**
+- Saves approximately 5 KB of flash memory with the same configuration
+
+**Disadvantages:**
+- Compilation configuration cannot be changed
+- Certain configurations may provide faster performance
+
+## Speed comparison
+
+The table below shows example decoding times for a JPEG image using various configurations:
+* Image size: 320 x 180 px
+* Output format: RGB565
+* CPU: ESP32-S3
+* CPU frequency: 240 MHz
+* SPI mode: DIO
+* Internal RAM used
+* Measured in 1000 retries
+
+| ROM used | JD_SZBUF | JD_FORMAT | JD_USE_SCALE | JD_TBLCLIP | JD_FASTDECODE | RAM buffer | Flash size | Approx. time |
+| :------: | :------: | :-------: | :----------: | :--------: | :-----------: | :--------: | :--------: | :----------: |
+|   YES    |    512   |   RGB888  |      1       |      1     |       0       |    3.1 kB  |    0 kB    |     52 ms    |    
+|   NO     |    512   |   RGB888  |      1       |      1     |       0       |    3.1 kB  |    5 kB    |     50 ms    |    
+|   NO     |    512   |   RGB888  |      1       |      0     |       0       |    3.1 kB  |    4 kB    |     68 ms    |     
+|   NO     |    512   |   RGB888  |      1       |      1     |       1       |    3.1 kB  |    5 kB    |     50 ms    |      
+|   NO     |    512   |   RGB888  |      1       |      0     |       1       |    3.1 kB  |    4 kB    |     62 ms    |   
+|   NO     |    512   |   RGB888  |      1       |      1     |       2       |   65.5 kB  |   5.5 kB   |     46 ms    |  
+|   NO     |    512   |   RGB888  |      1       |      0     |       2       |   65.5 kB  |   4.5 kB   |     59 ms    |  
+|   NO     |    512   |   RGB565  |      1       |      1     |       0       |    5 kB    |    5 kB    |     60 ms    |     
+|   NO     |    512   |   RGB565  |      1       |      1     |       1       |    5 kB    |    5 kB    |     59 ms    |     
+|   NO     |    512   |   RGB565  |      1       |      1     |       2       |   65.5 kB  |   5.5 kB   |     56 ms    |     
+
+## Add to project
+
+Packages from this repository are uploaded to [Espressif's component service](https://components.espressif.com/).
+You can add them to your project via `idf.py add-dependancy`, e.g. 
+```
+    idf.py add-dependency esp_jpeg==1.0.0
+```
+
+Alternatively, you can create `idf_component.yml`. More is in [Espressif's documentation](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/tools/idf-component-manager.html).
+
+## Example use
+
+Here is example of usage. This calling is **blocking**.
+
+```
+esp_jpeg_image_cfg_t jpeg_cfg = {
+    .indata = (uint8_t *)jpeg_img_buf,
+    .indata_size = jpeg_img_buf_size,
+    .outbuf = out_img_buf,
+    .outbuf_size = out_img_buf_size,
+    .out_format = JPEG_IMAGE_OUT_FORMAT_RGB565,
+    .out_scale = JPEG_IMAGE_SCALE_0,
+    .flags = {
+        .swap_color_bytes = 1,
+    }
+};
+esp_jpeg_image_output_t outimg;
+
+esp_jpeg_decode(&jpeg_cfg, &outimg);
+```