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author | Silas Bartha <silas@exvacuum.dev> | 2024-05-27 11:18:36 -0400 |
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committer | Silas Bartha <silas@exvacuum.dev> | 2024-05-27 11:18:36 -0400 |
commit | 16d1838e5bca2e90ca7cf8584a786b84fc409708 (patch) | |
tree | cf24077cd48b1c9fd1119fd7b7097a32660071e5 /src/lossless/champleve.rs |
Initial Commit
Diffstat (limited to 'src/lossless/champleve.rs')
-rw-r--r-- | src/lossless/champleve.rs | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/src/lossless/champleve.rs b/src/lossless/champleve.rs new file mode 100644 index 0000000..948408c --- /dev/null +++ b/src/lossless/champleve.rs @@ -0,0 +1,139 @@ +use std::cmp::Ordering; + +use image::{ColorType, DynamicImage, GenericImageView, Pixel}; +use thiserror::Error; + +use crate::codec::Codec; + +#[derive(Debug)] +pub struct ChampleveCodec; + +impl Codec for ChampleveCodec { + type Carrier = DynamicImage; + type Payload = Vec<u8>; + type Output = Self::Carrier; + type Error = ChampleveError; + + fn encode(&self, carrier: impl Into<Self::Carrier>, payload: impl Into<Self::Payload>) -> Result<Self::Output, Self::Error> { + let mut image: DynamicImage = carrier.into(); + let payload: Vec<u8> = payload.into(); + + if image.pixels().count() < payload.len() { + return Err(ChampleveError::PayloadTooBig); + } + + let mut payload_iter = payload.iter(); + + match image { + DynamicImage::ImageRgba8(ref mut image) => { + for pixel in image.pixels_mut() { + if let Some(payload_byte) = payload_iter.next() { + encode_pixel(pixel, *payload_byte, false); + } else { + encode_pixel(pixel, 0, true); + } + } + }, + DynamicImage::ImageRgb8(ref mut image) => { + for pixel in image.pixels_mut() { + if let Some(payload_byte) = payload_iter.next() { + encode_pixel(pixel, *payload_byte, false); + } else { + encode_pixel(pixel, 0, true); + } + } + }, + _ => return Err(ChampleveError::UnsupportedFormat { format: image.color() }) + } + + Ok(image) + } + + fn decode(&self, carrier: impl Into<Self::Output>) -> Result<(Self::Carrier, Self::Payload), ChampleveError> { + let mut image: DynamicImage = carrier.into(); + let mut payload: Vec<u8> = Vec::new(); + + match image { + DynamicImage::ImageRgba8(ref mut image) => { + for pixel in image.pixels_mut() { + if let Some(payload_byte) = decode_pixel(pixel) { + payload.push(payload_byte); + } else { + break; + } + } + }, + DynamicImage::ImageRgb8(ref mut image) => { + for pixel in image.pixels_mut() { + if let Some(payload_byte) = decode_pixel(pixel) { + payload.push(payload_byte); + } else { + break; + } + } + }, + _ => return Err(ChampleveError::UnsupportedFormat { format: image.color() }) + } + + Ok((image, payload)) + } +} + +fn encode_pixel<P: Pixel<Subpixel = u8>>(pixel: &mut P, payload_byte: u8, end_of_data: bool) { + let mut bits_remaining: i32 = 8; + for channel in pixel.channels_mut() { + *channel &= 0b11111000; + bits_remaining -= 3; + if bits_remaining <= -3 { + break; + } + + let mask = match bits_remaining.cmp(&0) { + Ordering::Less => payload_byte << -bits_remaining, + _ => payload_byte >> bits_remaining, + } & 0b00000111; + + *channel |= mask; + } + + // Add end-of-data marker to final bit if necessary + if end_of_data { + *pixel.channels_mut().last_mut().unwrap() |= 1; + } +} + +fn decode_pixel<P: Pixel<Subpixel = u8>>(pixel: &mut P) -> Option<u8> { + + // Final bit as end-of-data marker + if pixel.channels().last().unwrap() & 1 == 1 { + return None; + } + + let mut bits_remaining: i32 = 8; + let mut payload_byte: u8 = 0; + for channel in pixel.channels_mut() { + bits_remaining -= 3; + if bits_remaining <= -3 { + break; + } + + let channel_bits = *channel & 0b00000111; + *channel &= 0b11111000; + let mask = match bits_remaining.cmp(&0) { + Ordering::Less => channel_bits >> -bits_remaining, + _ => channel_bits << bits_remaining, + }; + payload_byte |= mask; + } + Some(payload_byte) +} + +#[derive(Error, Debug)] +pub enum ChampleveError { + #[error("Payload is too big for the carrier. Choose a smaller payload or an image with greater pixel dimensions.")] + PayloadTooBig, + #[error("Specified image format ({format:?}) is unsupported.")] + UnsupportedFormat { + format: ColorType + }, +} |