ESP_NEW_JPEG

ESP_NEW_JPEG is Espressif's lightweight JPEG encoder and decoder library. The memory and CPU loading are optimized to make better use of Espressif chips.

Features

Encoder

• Support variety of width and height to encoder
• Support RGB888 RGBA YCbYCr YCbY2YCrY2 GRAY pixel format
• Support YUV444 YUV422 YUV420 subsampling
• Support quality(1-100)
• Support 0 90 180 270 degree clockwise rotation, under the follow cases
  1. src_type = JPEG_PIXEL_FORMAT_YCbYCr, subsampling = JPEG_SUBSAMPLE_420 and width and height are multiply of 16
  2. src_type = JPEG_PIXEL_FORMAT_YCbYCr, subsampling = JPEG_SUBSAMPLE_GRAY and width and height are multiply of 8
• Support mono-task and dual-task
• Support two mode encoder, respectively one image encoder and block encoder

Decoder

• Support variety of width and height to decoder
• Support one and three channels decoder
• Support RGB888 RGB565(big endian) RGB565(little endian) CbYCrY pixel format output
• Support 0 90 180 270 degree clockwise rotation, under width and height are multiply of 8
• Support clipper and scale, under width and height are multiply of 8
• Support two mode decoder, respectively one image decoder and block decoder

Performance

Test on chip ESP32-S3

Encoder

For mono task encoder, the consume memory(10 kByte DRAM) is constant.

When dual task encoder in enabled, the wider the image, the more memory is consumed.

Decoder

The consume memory(10 kByte DRAM) is constant.

Rotate JPEG_ROTATE_0D cases:

Rotate JPEG_ROTATE_90D cases:

Test on chip ESP32-S2

Encoder

Only support mono task. The consume memory(10 kByte DRAM) is constant.

Decoder

The consume memory(10 kByte DRAM) is constant.

Rotate JPEG_ROTATE_0D cases:

Rotate JPEG_ROTATE_90D cases:

Usage

Please refer to the test_app folder for more details on API usage.

• test_app/main/test_encoder.c for encoder
  • Encode a single picture
  • Encode a single picture with block encoder API
• test_app/main/test_decoder.c for decoder
  • Decode a single JPEG picture
  • Decode a single JPEG picture with block deocder API
  • Decode JPEG stream of the same size

FAQ

1. Does ESP_NEW_JPEG support decoding progressive JPEG?

No, ESP_NEW_JPEG only support decoding baseline JPEG.

You can use the following code to check if the image is progressive JPEG. Output 1 means progressive JPEG, 0 means baseline JPEG.

```bash
python
>>> from PIL import Image
>>> Image.open("file_name.jpg").info.get('progressive', 0)
```

1. Why does the output image appear misaligned?

The issue typically occurs when a few columns of the image on the far left or right side appear on the opposite side. If you are using the ESP32-S3, a possible cause is that the output buffer of decoder or the input buffer of encoder is not 16-byte aligned. Please use the jpeg_calloc_align function to allocate buffer.

1. How can I use a simpler method to check if the encoder's output is correct?

You can use the following code to directly print the output JPEG data. Copy the output data, paste it into a hex editor, and save it as a .jpg file.

```c
for (int i = 0; i < out_len; i++) {
    printf("%02x", outbuf[i]);
}
printf("\n");
```

Supported chip

The following table shows the support of ESP_NEW_JPEG for Espressif SoCs. The "✔" means supported, and the "✖" means not supported.