Stable-Diffusion-v2.1 Example

This document explains how to use the QAI AppBuilder Python API to perform inference with the Stable-Diffusion-v2.1 text-to-image model using the Qualcomm® Hexagon™ Processor (NPU).

Supported Devices

Device	SoC
Fogwise® AIRbox Q900	QCS9075

Install QAI AppBuilder

tip

1. Please install QAI AppBuilder according to the QAI AppBuilder Installation Guide.

2. Please configure the ADSP environment variables according to Configuring ADSP Environment Variables.

Run Example

Install Dependencies

Device

pip3 install requests tqdm qai-hub py3_wget opencv-python torch torchvision matplotlib easyocr qai_hub_models transformers diffusers

Run the Script

• Navigate to the example directory

  QCS9075

  Device

  cd ai-engine-direct-helper/samples/python

• Execute inference

  Device

  python3 stable_diffusion_v2_1/stable_diffusion_v2_1.py --prompt spectacular view of northern lights from Alaska

  python3 stable_diffusion_v2_1/stable_diffusion_v2_1.py --prompt spectacular view of northern lights from Alaska
  /prj/qct/webtech_scratch20/mlg_user_admin/qaisw_source_repo/rel/qairt-2.37.1/point_release/SNPE_SRC/avante-tools/prebuilt/dsp/hexagon-sdk-5.5.5/ipc/fastrpc/rpcmem/src/rpcmem_android.c:38:dummy call to rpcmem_init, rpcmem APIs will be used from libxdsprpc
  Step 0 Running...
  Step 1 Running...
  Step 2 Running...
  Step 3 Running...
  Step 4 Running...
  Step 5 Running...
  Step 6 Running...
  Step 7 Running...
  Step 8 Running...
  Step 9 Running...
  Step 10 Running...
  Step 11 Running...
  Step 12 Running...
  Step 13 Running...
  Step 14 Running...
  Step 15 Running...
  Step 16 Running...
  Step 17 Running...
  Step 18 Running...
  Step 19 Running...
  /mnt/ssd/qualcomm/702/zzf_fork/test/ai-engine-direct-helper/samples/python/stable_diffusion_v2_1/stable_diffusion_v2_1.py:275: DeprecationWarning: 'mode' parameter is deprecated and will be removed in Pillow 13 (2026-10-15)
    output_image = Image.fromarray(output_image, mode="RGB")
  Image saved to '/mnt/ssd/qualcomm/702/zzf_fork/test/ai-engine-direct-helper/samples/python/stable_diffusion_v2_1/images/2025_10_30_05_46_28_2081127356_512.jpg'
  time consumes for inference 4.454082250595093(s)
  /usr/bin/xdg-open: 882: www-browser: not found
  /usr/bin/xdg-open: 882: links2: not found
   <W> Logs will be sent to the system's default channel
  /usr/bin/xdg-open: 882: elinks: not found
  /usr/bin/xdg-open: 882: links: not found
  /usr/bin/xdg-open: 882: lynx: not found
  /usr/bin/xdg-open: 882: w3m: not found
  xdg-open: no method available for opening '/tmp/tmp0ci7lglx.PNG'
   <W> Logs will be sent to the system's default channel
  /prj/qct/webtech_scratch20/mlg_user_admin/qaisw_source_repo/rel/qairt-2.37.1/point_release/SNPE_SRC/avante-tools/prebuilt/dsp/hexagon-sdk-5.5.5/ipc/fastrpc/rpcmem/src/rpcmem_android.c:42:dummy call to rpcmem_deinit, rpcmem APIs will be used from libxdsprpc

  

  Output image