git.stevedylan.dev

Merge pull request #9 from stevedylandev/chore/shrink-preserve-exif-data 936aa399

chore: preserve exif data while removing geo data

Steve Simkins · 2026-04-04 20:02 3 file(s) · +114 −7

Cargo.lock +13 −1


[[package]]
name = "cellar"
version = "0.1.1"
version = "0.1.2"
dependencies = [
 "andromeda-auth",
 "askama 0.15.6",

dependencies = [
 "byteorder-lite",
 "quick-error",
]

[[package]]
name = "img-parts"
version = "0.3.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "6b4e24cfdc6f897b582508e3c382eaf5378076898f80500a80d10d761ae85e90"
dependencies = [
 "bytes",
 "crc32fast",
 "miniz_oxide",
]

[[package]]

 "askama 0.15.6",
 "axum",
 "image",
 "img-parts",
 "serde",
 "tokio",
 "tower-http",

apps/shrink/Cargo.toml +1 −0

16	16		tracing-subscriber = { workspace = true }
17	17		askama = "0.15"
18	18		image = "0.25"
	19	+	img-parts = "0.3"

apps/shrink/src/server.rs +100 −6

    routing::{get, post},
};
use axum::extract::DefaultBodyLimit;
use img_parts::ImageEXIF;
use img_parts::jpeg::Jpeg;
use tower_http::services::ServeDir;

#[derive(Template)]

                    .map_err(|e| (StatusCode::BAD_REQUEST, format!("Failed to read width: {}", e)))?;
                width = text.parse::<u32>().unwrap_or(0);
            }
            _ => {}
_ => {}
        }
    }

    let file_data = file_data.ok_or((StatusCode::BAD_REQUEST, "No file provided".to_string()))?;

    let result = tokio::task::spawn_blocking(move || compress_image(&file_data, quality, width))
        .await
        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("Task failed: {}", e)))?
        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("Compression failed: {}", e)))?;
    let result =
        tokio::task::spawn_blocking(move || compress_image(&file_data, quality, width))
            .await
            .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, format!("Task failed: {}", e)))?
            .map_err(|e| {
                (
                    StatusCode::INTERNAL_SERVER_ERROR,
                    format!("Compression failed: {}", e),
                )
            })?;

    let download_name = build_download_filename(&original_filename, "jpg");


}

fn compress_image(data: &[u8], quality: u8, width: u32) -> Result<Vec<u8>, String> {
    // Extract EXIF from original before re-encoding destroys it
    let original_exif = Jpeg::from_bytes(data.to_vec().into())
        .ok()
        .and_then(|j| j.exif().map(|e| e.to_vec()));

    let img =
        image::load_from_memory(data).map_err(|e| format!("Failed to decode image: {}", e))?;


    img.write_with_encoder(encoder)
        .map_err(|e| format!("JPEG encoding failed: {}", e))?;

    Ok(output)
    // Re-inject EXIF into the compressed output (always strip GPS data)
    if let Some(exif_bytes) = original_exif {
        let exif = strip_gps_from_exif(&exif_bytes);

        let mut out_jpeg = Jpeg::from_bytes(output.into())
            .map_err(|e| format!("Failed to parse compressed JPEG: {}", e))?;
        out_jpeg.set_exif(Some(exif.into()));
        let mut final_output = Vec::new();
        out_jpeg
            .encoder()
            .write_to(&mut final_output)
            .map_err(|e| format!("Failed to write JPEG with EXIF: {}", e))?;
        Ok(final_output)
    } else {
        Ok(output)
    }
}

/// Strips GPS data from raw EXIF bytes by zeroing the GPS IFD entry count.
/// Preserves all other metadata (camera, lens, settings, etc.) and offsets.
fn strip_gps_from_exif(exif: &[u8]) -> Vec<u8> {
    let mut data = exif.to_vec();

    // img-parts strips the "Exif\0\0" prefix, so bytes start with TIFF header (II/MM)
    let tiff_start = if data.len() >= 14 && &data[0..4] == b"Exif" {
        6
    } else if data.len() >= 8 && (&data[0..2] == b"II" || &data[0..2] == b"MM") {
        0
    } else {
        return data;
    };
    let big_endian = &data[tiff_start..tiff_start + 2] == b"MM";

    let read_u16 = |d: &[u8], off: usize| -> u16 {
        if big_endian {
            u16::from_be_bytes([d[off], d[off + 1]])
        } else {
            u16::from_le_bytes([d[off], d[off + 1]])
        }
    };

    let read_u32 = |d: &[u8], off: usize| -> u32 {
        if big_endian {
            u32::from_be_bytes([d[off], d[off + 1], d[off + 2], d[off + 3]])
        } else {
            u32::from_le_bytes([d[off], d[off + 1], d[off + 2], d[off + 3]])
        }
    };

    // IFD0 offset (relative to TIFF start)
    let ifd0_rel = read_u32(&data, tiff_start + 4) as usize;
    let ifd0_off = tiff_start + ifd0_rel;
    if ifd0_off + 2 > data.len() {
        return data;
    }

    let entry_count = read_u16(&data, ifd0_off) as usize;

    for i in 0..entry_count {
        let entry_off = ifd0_off + 2 + i * 12;
        if entry_off + 12 > data.len() {
            break;
        }
        let tag = read_u16(&data, entry_off);
        if tag == 0x8825 {
            // GPS IFD pointer — read the offset, then zero out the GPS IFD entry count
            let gps_ifd_rel = read_u32(&data, entry_off + 8) as usize;
            let gps_ifd_off = tiff_start + gps_ifd_rel;
            if gps_ifd_off + 2 <= data.len() {
                let zero = if big_endian {
                    0u16.to_be_bytes()
                } else {
                    0u16.to_le_bytes()
                };
                data[gps_ifd_off] = zero[0];
                data[gps_ifd_off + 1] = zero[1];
            }
            break;
        }
    }

    data
}

fn build_download_filename(original: &str, new_ext: &str) -> String {

644	644
645	645		[[package]]
646	646		name = "cellar"
647		-	version = "0.1.1"
	647	+	version = "0.1.2"
648	648		dependencies = [
649	649		"andromeda-auth",
650	650		"askama 0.15.6",

1915	1915		dependencies = [
1916	1916		"byteorder-lite",
1917	1917		"quick-error",
	1918	+	]
	1919	+
	1920	+	[[package]]
	1921	+	name = "img-parts"
	1922	+	version = "0.3.3"
	1923	+	source = "registry+https://github.com/rust-lang/crates.io-index"
	1924	+	checksum = "6b4e24cfdc6f897b582508e3c382eaf5378076898f80500a80d10d761ae85e90"
	1925	+	dependencies = [
	1926	+	"bytes",
	1927	+	"crc32fast",
	1928	+	"miniz_oxide",
1918	1929		]
1919	1930
1920	1931		[[package]]

3923	3934		"askama 0.15.6",
3924	3935		"axum",
3925	3936		"image",
	3937	+	"img-parts",
3926	3938		"serde",
3927	3939		"tokio",
3928	3940		"tower-http",

7	7		routing::{get, post},
8	8		};
9	9		use axum::extract::DefaultBodyLimit;
	10	+	use img_parts::ImageEXIF;
	11	+	use img_parts::jpeg::Jpeg;
10	12		use tower_http::services::ServeDir;
11	13
12	14		#[derive(Template)]

64	66		.map_err(\|e\| (StatusCode::BAD_REQUEST, format!("Failed to read width: {}", e)))?;
65	67		width = text.parse::<u32>().unwrap_or(0);
66	68		}
67		-	_ => {}
	69	+	_ => {}
68	70		}
69	71		}
70	72
71	73		let file_data = file_data.ok_or((StatusCode::BAD_REQUEST, "No file provided".to_string()))?;
72	74
73		-	let result = tokio::task::spawn_blocking(move \|\| compress_image(&file_data, quality, width))
74		-	.await
75		-	.map_err(\|e\| (StatusCode::INTERNAL_SERVER_ERROR, format!("Task failed: {}", e)))?
76		-	.map_err(\|e\| (StatusCode::INTERNAL_SERVER_ERROR, format!("Compression failed: {}", e)))?;
	75	+	let result =
	76	+	tokio::task::spawn_blocking(move \|\| compress_image(&file_data, quality, width))
	77	+	.await
	78	+	.map_err(\|e\| (StatusCode::INTERNAL_SERVER_ERROR, format!("Task failed: {}", e)))?
	79	+	.map_err(\|e\| {
	80	+	(
	81	+	StatusCode::INTERNAL_SERVER_ERROR,
	82	+	format!("Compression failed: {}", e),
	83	+	)
	84	+	})?;
77	85
78	86		let download_name = build_download_filename(&original_filename, "jpg");
79	87

92	100		}
93	101
94	102		fn compress_image(data: &[u8], quality: u8, width: u32) -> Result<Vec<u8>, String> {
	103	+	// Extract EXIF from original before re-encoding destroys it
	104	+	let original_exif = Jpeg::from_bytes(data.to_vec().into())
	105	+	.ok()
	106	+	.and_then(\|j\| j.exif().map(\|e\| e.to_vec()));
	107	+
95	108		let img =
96	109		image::load_from_memory(data).map_err(\|e\| format!("Failed to decode image: {}", e))?;
97	110

108	121		img.write_with_encoder(encoder)
109	122		.map_err(\|e\| format!("JPEG encoding failed: {}", e))?;
110	123
111		-	Ok(output)
	124	+	// Re-inject EXIF into the compressed output (always strip GPS data)
	125	+	if let Some(exif_bytes) = original_exif {
	126	+	let exif = strip_gps_from_exif(&exif_bytes);
	127	+
	128	+	let mut out_jpeg = Jpeg::from_bytes(output.into())
	129	+	.map_err(\|e\| format!("Failed to parse compressed JPEG: {}", e))?;
	130	+	out_jpeg.set_exif(Some(exif.into()));
	131	+	let mut final_output = Vec::new();
	132	+	out_jpeg
	133	+	.encoder()
	134	+	.write_to(&mut final_output)
	135	+	.map_err(\|e\| format!("Failed to write JPEG with EXIF: {}", e))?;
	136	+	Ok(final_output)
	137	+	} else {
	138	+	Ok(output)
	139	+	}
	140	+	}
	141	+
	142	+	/// Strips GPS data from raw EXIF bytes by zeroing the GPS IFD entry count.
	143	+	/// Preserves all other metadata (camera, lens, settings, etc.) and offsets.
	144	+	fn strip_gps_from_exif(exif: &[u8]) -> Vec<u8> {
	145	+	let mut data = exif.to_vec();
	146	+
	147	+	// img-parts strips the "Exif\0\0" prefix, so bytes start with TIFF header (II/MM)
	148	+	let tiff_start = if data.len() >= 14 && &data[0..4] == b"Exif" {
	149	+	6
	150	+	} else if data.len() >= 8 && (&data[0..2] == b"II" \|\| &data[0..2] == b"MM") {
	151	+	0
	152	+	} else {
	153	+	return data;
	154	+	};
	155	+	let big_endian = &data[tiff_start..tiff_start + 2] == b"MM";
	156	+
	157	+	let read_u16 = \|d: &[u8], off: usize\| -> u16 {
	158	+	if big_endian {
	159	+	u16::from_be_bytes([d[off], d[off + 1]])
	160	+	} else {
	161	+	u16::from_le_bytes([d[off], d[off + 1]])
	162	+	}
	163	+	};
	164	+
	165	+	let read_u32 = \|d: &[u8], off: usize\| -> u32 {
	166	+	if big_endian {
	167	+	u32::from_be_bytes([d[off], d[off + 1], d[off + 2], d[off + 3]])
	168	+	} else {
	169	+	u32::from_le_bytes([d[off], d[off + 1], d[off + 2], d[off + 3]])
	170	+	}
	171	+	};
	172	+
	173	+	// IFD0 offset (relative to TIFF start)
	174	+	let ifd0_rel = read_u32(&data, tiff_start + 4) as usize;
	175	+	let ifd0_off = tiff_start + ifd0_rel;
	176	+	if ifd0_off + 2 > data.len() {
	177	+	return data;
	178	+	}
	179	+
	180	+	let entry_count = read_u16(&data, ifd0_off) as usize;
	181	+
	182	+	for i in 0..entry_count {
	183	+	let entry_off = ifd0_off + 2 + i * 12;
	184	+	if entry_off + 12 > data.len() {
	185	+	break;
	186	+	}
	187	+	let tag = read_u16(&data, entry_off);
	188	+	if tag == 0x8825 {
	189	+	// GPS IFD pointer — read the offset, then zero out the GPS IFD entry count
	190	+	let gps_ifd_rel = read_u32(&data, entry_off + 8) as usize;
	191	+	let gps_ifd_off = tiff_start + gps_ifd_rel;
	192	+	if gps_ifd_off + 2 <= data.len() {
	193	+	let zero = if big_endian {
	194	+	0u16.to_be_bytes()
	195	+	} else {
	196	+	0u16.to_le_bytes()
	197	+	};
	198	+	data[gps_ifd_off] = zero[0];
	199	+	data[gps_ifd_off + 1] = zero[1];
	200	+	}
	201	+	break;
	202	+	}
	203	+	}
	204	+
	205	+	data
112	206		}
113	207
114	208		fn build_download_filename(original: &str, new_ext: &str) -> String {