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Fix alternative filter modes

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Fixes #9
This commit is contained in:
Joshua Holmer 2016-03-03 13:52:52 -05:00
parent 2edf54c9f4
commit 9a8c3f64b9
1 changed files with 14 additions and 16 deletions
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30
src/png.rs
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@ -343,8 +343,7 @@ impl PngData {
pub fn unfilter_image(&self) -> Vec<u8> {
let mut unfiltered = Vec::with_capacity(self.raw_data.len());
let tmp = self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel();
// Round up without converting to float
let bpp = (tmp + tmp % 8) >> 3;
let bpp = ((tmp as f32) / 8f32).ceil() as usize;
let mut last_line: Vec<u8> = vec![];
for line in self.scan_lines() {
unfiltered.push(0);
@ -355,7 +354,7 @@ impl PngData {
1 => {
let mut data = Vec::with_capacity(line.data.len());
for (i, byte) in line.data.iter().enumerate() {
match i.checked_sub(bpp as usize) {
match i.checked_sub(bpp) {
Some(x) => {
let b = data[x];
data.push(byte.wrapping_add(b))
@ -382,7 +381,7 @@ impl PngData {
let mut data = Vec::with_capacity(line.data.len());
for (i, byte) in line.data.iter().enumerate() {
if last_line.is_empty() {
match i.checked_sub(bpp as usize) {
match i.checked_sub(bpp) {
Some(x) => {
let b = data[x];
data.push(byte.wrapping_add(b >> 1))
@ -390,7 +389,7 @@ impl PngData {
None => data.push(*byte),
};
} else {
match i.checked_sub(bpp as usize) {
match i.checked_sub(bpp) {
Some(x) => {
let b = data[x];
data.push(byte.wrapping_add(
@ -408,7 +407,7 @@ impl PngData {
let mut data = Vec::with_capacity(line.data.len());
for (i, byte) in line.data.iter().enumerate() {
if last_line.is_empty() {
match i.checked_sub(bpp as usize) {
match i.checked_sub(bpp) {
Some(x) => {
let b = data[x];
data.push(byte.wrapping_add(b))
@ -416,7 +415,7 @@ impl PngData {
None => data.push(*byte),
};
} else {
match i.checked_sub(bpp as usize) {
match i.checked_sub(bpp) {
Some(x) => {
let b = data[x];
data.push(byte.wrapping_add(paeth_predictor(b,
@ -438,8 +437,7 @@ impl PngData {
pub fn filter_image(&self, filter: u8) -> Vec<u8> {
let mut filtered = Vec::with_capacity(self.raw_data.len());
let tmp = self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel();
// Round up without converting to float
let bpp = (tmp + tmp % 8) >> 3;
let bpp = ((tmp as f32) / 8f32).ceil() as usize;
let mut last_line: Vec<u8> = vec![];
// We could try a different filter method for each line
// But that would be prohibitively slow and probably not provide much benefit
@ -454,7 +452,7 @@ impl PngData {
}
1 => {
for (i, byte) in line.data.iter().enumerate() {
filtered.push(match i.checked_sub(bpp as usize) {
filtered.push(match i.checked_sub(bpp) {
Some(x) => byte.wrapping_sub(line.data[x]),
None => *byte,
});
@ -472,12 +470,12 @@ impl PngData {
3 => {
for (i, byte) in line.data.iter().enumerate() {
if last_line.is_empty() {
filtered.push(match i.checked_sub(bpp as usize) {
filtered.push(match i.checked_sub(bpp) {
Some(x) => byte.wrapping_sub(line.data[x] >> 1),
None => *byte,
});
} else {
filtered.push(match i.checked_sub(bpp as usize) {
filtered.push(match i.checked_sub(bpp) {
Some(x) => byte.wrapping_sub(
((line.data[x] as u16 + last_line[i] as u16) >> 1) as u8
),
@ -489,12 +487,12 @@ impl PngData {
4 => {
for (i, byte) in line.data.iter().enumerate() {
if last_line.is_empty() {
filtered.push(match i.checked_sub(bpp as usize) {
filtered.push(match i.checked_sub(bpp) {
Some(x) => byte.wrapping_sub(line.data[x]),
None => *byte,
});
} else {
filtered.push(match i.checked_sub(bpp as usize) {
filtered.push(match i.checked_sub(bpp) {
Some(x) => {
byte.wrapping_sub(paeth_predictor(line.data[x],
last_line[i],
@ -520,7 +518,7 @@ impl PngData {
let mut line_4 = Vec::with_capacity(line.data.len());
for (i, byte) in line.data.iter().enumerate() {
if last_line.is_empty() {
match i.checked_sub(bpp as usize) {
match i.checked_sub(bpp) {
Some(x) => {
line_1.push(byte.wrapping_sub(line.data[x]));
line_2.push(*byte);
@ -535,7 +533,7 @@ impl PngData {
}
}
} else {
match i.checked_sub(bpp as usize) {
match i.checked_sub(bpp) {
Some(x) => {
line_1.push(byte.wrapping_sub(line.data[x]));
line_2.push(byte.wrapping_sub(last_line[i]));