Support png image and resize image with 64 pixels in img2img mode

[delldu]

1) Before modification

./build/bin/sd --mode img2img --model models/sdxl_turbo_q8_0.gguf -p "red shoes" -i images/shose.png --strength 0.75 --cfg-scale 1.8 --steps 10 -o output_img2img_sdxl.png

output error message

input image must be a 3 channels RGB image, but got 4 channels

2) After modification

./build/bin/sd --mode img2img --model models/sdxl_turbo_q8_0.gguf -p "red shoes" -i images/shose.png --strength 0.75 --cfg-scale 1.8 --steps 10 -o output_img2img_sdxl.png

Create output_img2img_sdxl OK.

[leejet]

Thank you for your contribution.