wehub-resource-sync
84 lines
3.8 KiB
Markdown
84 lines
3.8 KiB
Markdown
| Supported Targets | ESP32-P4 | ESP32-S31 |
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# JPEG decode example
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## Overview
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This example demonstrates how to use the JPEG hardware decoder to decode one embedded JPEG image into `RGB888` raw bytes in default `BGR24` order.
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The example performs:
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- Embedding `main/assets/image.jpg` into the application image
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- Letting the JPEG decoder read the embedded JPEG bitstream directly from flash
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- Parsing the JPEG header with `jpeg_decoder_get_info()`
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- Decoding the image into an `RGB888` output buffer with default `BGR24` byte order
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- Allocating the output buffer for padded dimensions when the JPEG block layout rounds width or height up to 16-pixel boundaries
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- Base64-encoding the decoded raw pixels and printing them with machine-parseable UART markers
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- Letting pytest rebuild `jpeg_decode_result.ppm` for inspection and compare it against `golden_output.ppm`
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## Hardware Required
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Any board based on a supported target can be used. No SD card or external storage setup is required.
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## Build and Flash
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Run `idf.py -p PORT flash monitor` to build, flash and monitor the project.
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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```text
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Loading embedded JPEG from flash...
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Embedded JPEG size: 43700 bytes
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JPEG header parsed: width=320 height=240
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Decoding JPEG -> RGB888...
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Decoded RGB888 size: 245760 bytes
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JPEG_DECODE_INFO width=320 height=240 padded_width=320 padded_height=256 format=RGB888 encoding=base64 size=245760
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JPEG_DECODE_BASE64_BEGIN
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JPEG_DECODE_BASE64 ...
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JPEG_DECODE_BASE64 ...
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JPEG_DECODE_BASE64_END
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JPEG decode demo done.
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```
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`padded_width` and `padded_height` report the actual decoded buffer dimensions. For JPEGs whose block layout pads the output to 16-pixel boundaries, these values can be larger than the visible `width` and `height`, so the output buffer must be sized for the padded image.
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## Pytest Regression Check
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The accompanying `pytest_jpeg_decode.py` script waits for the `JPEG_DECODE_INFO` and `JPEG_DECODE_BASE64` markers, reconstructs the decoded raw pixel output, crops away padded rows, and saves the visible image as:
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- `dut.logdir/jpeg_decode_result.ppm`
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The test writes the `PPM` file and compares it with `golden_output.ppm`. This makes the example both a functional regression test and a host-side artifact generator for inspection.
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## Running Pytest Locally And Viewing The Image
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To run the pytest helper locally on hardware, build the example for your target first, then invoke the test script with the target and serial port:
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```bash
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idf.py set-target esp32p4 build
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pytest --target esp32p4 --port PORT pytest_jpeg_decode.py
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```
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Replace `esp32p4` with another supported target such as `esp32s31` when needed.
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`pytest-embedded` stores per-test logs under `$IDF_PATH/pytest-embedded/`. The script writes the reconstructed image to `jpeg_decode_result.ppm` inside that test log directory, so after the test finishes you can open the generated `PPM` file locally with an image viewer that supports `PPM` to inspect the decoded output.
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## Replacing The Embedded JPEG Asset
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If you want to try another input image, replace:
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- `main/assets/image.jpg`
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Keep the replacement as a baseline JPEG with the same general scale if you want UART log volume and test runtime to stay small.
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After replacing the asset, rerun the example and update `golden_output.ppm` from the generated `dut.logdir/jpeg_decode_result.ppm` artifact if the new output should become the expected result.
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## Troubleshooting
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(For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you as soon as possible.)
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