Fix i1 png reading? & tests (#17)

* fix i1 png reading

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "pigment64"
-version = "0.4.1"
+version = "0.4.2"
 edition = "2021"
 description = "A library for handling conversion between N64 texture formats and modern image formats"
 repository = "https://github.com/decompals/pigment64"

src/image/png_image.rs

@@ -147,13 +147,18 @@ impl PNGImage {
         if let (ColorType::Grayscale, BitDepth::One) = (self.color_type, self.bit_depth) {
             writer.write_all(&self.data).map_err(Into::into)
         } else {
-            let mut i8_data = vec![0; self.data.len() * 8];
-            self.as_i8(&mut i8_data.as_mut_slice())?;
+            // Convert to i8 and then convert to i1
+            let mut i8_data = Vec::new();
+            self.as_i8(&mut i8_data)?;
 
-            for chunk in i8_data.chunks_exact(8) {
+            for pixels in i8_data.chunks_exact(8) {
+                // Combine the 8 pixels into a single byte
                 let mut byte = 0;
-                for (i, pixel) in chunk.iter().copied().enumerate() {
-                    byte |= ((pixel > 127) as u8) << (7 - i);
+                for (i, pixel) in pixels.iter().copied().enumerate() {
+                    // If its intensity is over half, set the bit
+                    if pixel > u8::MAX / 2 {
+                        byte |= 1 << (7 - i);
+                    }
                 }
                 writer.write_u8(byte)?;
             }

tests/native_image.rs

@@ -27,6 +27,23 @@ fn ci4() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn i1() -> Result<()> {
+    let original_bytes: &[u8] = include_bytes!("i1.png.bin");
+    let image = NativeImage::read(original_bytes, ImageType::I1, 72, 72)?;
+
+    let mut output: Vec<u8> = Vec::new();
+    image.as_png(&mut output, None)?;
+
+    // convert the png back to a native image
+    let image = PNGImage::read(output.as_slice())?;
+    let mut output_bytes: Vec<u8> = Vec::new();
+    image.as_i1(&mut output_bytes)?;
+
+    assert_eq!(output_bytes, original_bytes);
+    Ok(())
+}
+
 #[test]
 fn i4() -> Result<()> {
     let original_bytes: &[u8] = include_bytes!("i4.png.bin");

tests/png_image.rs

@@ -28,6 +28,19 @@ fn ci4() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn i1() -> Result<()> {
+    let input_bytes: &[u8] = include_bytes!("i1.png");
+    let image = PNGImage::read(input_bytes)?;
+
+    let expected_bytes = include_bytes!("i1.png.bin");
+    let mut output: Vec<u8> = Vec::new();
+    image.as_i1(&mut output)?;
+
+    assert_eq!(output, expected_bytes);
+    Ok(())
+}
+
 #[test]
 fn i4() -> Result<()> {
     let input_bytes: &[u8] = include_bytes!("i4.png");