From e52f1ec02af159fc16541ed8e7e134de805d9758 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kornel=20Lesi=C5=84ski?= <kornel@geekhood.net>
Date: Wed, 14 Nov 2018 21:55:37 +0000
Subject: [PATCH] Use integer math when rounding

---
 src/interlace.rs | 5 ++---
 src/png/mod.rs   | 6 ++----
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/interlace.rs b/src/interlace.rs
index cdf20a2d..e5a59129 100644
--- a/src/interlace.rs
+++ b/src/interlace.rs
@@ -93,9 +93,8 @@ pub fn deinterlace_image(png: &mut PngData) {
     let mut current_y: usize = pass_constants.y_shift as usize;
     for line in png.scan_lines() {
         let bit_vec = BitVec::from_bytes(&line.data);
-        let bits_in_line = ((png.ihdr_data.width - u32::from(pass_constants.x_shift)) as f32
-            / f32::from(pass_constants.x_step)).ceil() as usize
-            * bits_per_pixel as usize;
+        let bits_in_line = ((png.ihdr_data.width - u32::from(pass_constants.x_shift) + u32::from(pass_constants.x_step) - 1)
+            / u32::from(pass_constants.x_step)) as usize * bits_per_pixel as usize;
         for (i, bit) in bit_vec.iter().enumerate() {
             // Avoid moving padded 0's into new image
             if i >= bits_in_line {
diff --git a/src/png/mod.rs b/src/png/mod.rs
index 9dbf8b4d..c3dc6fde 100644
--- a/src/png/mod.rs
+++ b/src/png/mod.rs
@@ -226,8 +226,7 @@ impl PngData {
     /// Reverse all filters applied on the image, returning an unfiltered IDAT bytestream
     pub fn unfilter_image(&self) -> Vec<u8> {
         let mut unfiltered = Vec::with_capacity(self.raw_data.len());
-        let bpp = ((f32::from(self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel())) / 8f32)
-            .ceil() as usize;
+        let bpp = ((self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel() + 7) / 8) as usize;
         let mut last_line: Vec<u8> = Vec::new();
         let mut last_pass = 1;
         for line in self.scan_lines() {
@@ -254,8 +253,7 @@ impl PngData {
     /// 5: All (heuristically pick the best filter for each line)
     pub fn filter_image(&self, filter: u8) -> Vec<u8> {
         let mut filtered = Vec::with_capacity(self.raw_data.len());
-        let bpp = ((f32::from(self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel())) / 8f32)
-            .ceil() as usize;
+        let bpp = ((self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel() + 7) / 8) as usize;
         let mut last_line: Vec<u8> = Vec::new();
         let mut last_pass: Option<u8> = None;
         for line in self.scan_lines() {