//! Common types shared between the encoder and decoder
use crate::text_metadata::{EncodableTextChunk, ITXtChunk, TEXtChunk, ZTXtChunk};
use crate::{chunk, encoder};
use io::Write;
use std::{borrow::Cow, convert::TryFrom, fmt, io};
/// Describes how a pixel is encoded.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum ColorType {
/// 1 grayscale sample.
Grayscale = 0,
/// 1 red sample, 1 green sample, 1 blue sample.
Rgb = 2,
/// 1 sample for the palette index.
Indexed = 3,
/// 1 grayscale sample, then 1 alpha sample.
GrayscaleAlpha = 4,
/// 1 red sample, 1 green sample, 1 blue sample, and finally, 1 alpha sample.
Rgba = 6,
}
impl ColorType {
/// Returns the number of samples used per pixel encoded in this way.
pub fn samples(self) -> usize {
self.samples_u8().into()
}
pub(crate) fn samples_u8(self) -> u8 {
use self::ColorType::*;
match self {
Grayscale | Indexed => 1,
Rgb => 3,
GrayscaleAlpha => 2,
Rgba => 4,
}
}
/// u8 -> Self. Temporary solution until Rust provides a canonical one.
pub fn from_u8(n: u8) -> Option<ColorType> {
match n {
0 => Some(ColorType::Grayscale),
2 => Some(ColorType::Rgb),
3 => Some(ColorType::Indexed),
4 => Some(ColorType::GrayscaleAlpha),
6 => Some(ColorType::Rgba),
_ => None,
}
}
pub(crate) fn checked_raw_row_length(self, depth: BitDepth, width: u32) -> Option<usize> {
// No overflow can occur in 64 bits, we multiply 32-bit with 5 more bits.
let bits = u64::from(width) * u64::from(self.samples_u8()) * u64::from(depth.into_u8());
TryFrom::try_from(1 + (bits + 7) / 8).ok()
}
pub(crate) fn raw_row_length_from_width(self, depth: BitDepth, width: u32) -> usize {
let samples = width as usize * self.samples();
1 + match depth {
BitDepth::Sixteen => samples * 2,
BitDepth::Eight => samples,
subbyte => {
let samples_per_byte = 8 / subbyte as usize;
let whole = samples / samples_per_byte;
let fract = usize::from(samples % samples_per_byte > 0);
whole + fract
}
}
}
pub(crate) fn is_combination_invalid(self, bit_depth: BitDepth) -> bool {
// Section 11.2.2 of the PNG standard disallows several combinations
// of bit depth and color type
((bit_depth == BitDepth::One || bit_depth == BitDepth::Two || bit_depth == BitDepth::Four)
&& (self == ColorType::Rgb
|| self == ColorType::GrayscaleAlpha
|| self == ColorType::Rgba))
|| (bit_depth == BitDepth::Sixteen && self == ColorType::Indexed)
}
}
/// Bit depth of the PNG file.
/// Specifies the number of bits per sample.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum BitDepth {
One = 1,
Two = 2,
Four = 4,
Eight = 8,
Sixteen = 16,
}
/// Internal count of bytes per pixel.
/// This is used for filtering which never uses sub-byte units. This essentially reduces the number
/// of possible byte chunk lengths to a very small set of values appropriate to be defined as an
/// enum.
#[derive(Debug, Clone, Copy)]
#[repr(u8)]
pub(crate) enum BytesPerPixel {
One = 1,
Two = 2,
Three = 3,
Four = 4,
Six = 6,
Eight = 8,
}
impl BitDepth {
/// u8 -> Self. Temporary solution until Rust provides a canonical one.
pub fn from_u8(n: u8) -> Option<BitDepth> {
match n {
1 => Some(BitDepth::One),
2 => Some(BitDepth::Two),
4 => Some(BitDepth::Four),
8 => Some(BitDepth::Eight),
16 => Some(BitDepth::Sixteen),
_ => None,
}
}
pub(crate) fn into_u8(self) -> u8 {
self as u8
}
}
/// Pixel dimensions information
#[derive(Clone, Copy, Debug)]
pub struct PixelDimensions {
/// Pixels per unit, X axis
pub xppu: u32,
/// Pixels per unit, Y axis
pub yppu: u32,
/// Either *Meter* or *Unspecified*
pub unit: Unit,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
/// Physical unit of the pixel dimensions
pub enum Unit {
Unspecified = 0,
Meter = 1,
}
impl Unit {
/// u8 -> Self. Temporary solution until Rust provides a canonical one.
pub fn from_u8(n: u8) -> Option<Unit> {
match n {
0 => Some(Unit::Unspecified),
1 => Some(Unit::Meter),
_ => None,
}
}
}
/// How to reset buffer of an animated png (APNG) at the end of a frame.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum DisposeOp {
/// Leave the buffer unchanged.
None = 0,
/// Clear buffer with the background color.
Background = 1,
/// Reset the buffer to the state before the current frame.
Previous = 2,
}
impl DisposeOp {
/// u8 -> Self. Using enum_primitive or transmute is probably the right thing but this will do for now.
pub fn from_u8(n: u8) -> Option<DisposeOp> {
match n {
0 => Some(DisposeOp::None),
1 => Some(DisposeOp::Background),
2 => Some(DisposeOp::Previous),
_ => None,
}
}
}
impl fmt::Display for DisposeOp {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let name = match *self {
DisposeOp::None => "DISPOSE_OP_NONE",
DisposeOp::Background => "DISPOSE_OP_BACKGROUND",
DisposeOp::Previous => "DISPOSE_OP_PREVIOUS",
};
write!(f, "{}", name)
}
}
/// How pixels are written into the buffer.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum BlendOp {
/// Pixels overwrite the value at their position.
Source = 0,
/// The new pixels are blended into the current state based on alpha.
Over = 1,
}
impl BlendOp {
/// u8 -> Self. Using enum_primitive or transmute is probably the right thing but this will do for now.
pub fn from_u8(n: u8) -> Option<BlendOp> {
match n {
0 => Some(BlendOp::Source),
1 => Some(BlendOp::Over),
_ => None,
}
}
}
impl fmt::Display for BlendOp {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let name = match *self {
BlendOp::Source => "BLEND_OP_SOURCE",
BlendOp::Over => "BLEND_OP_OVER",
};
write!(f, "{}", name)
}
}
/// Frame control information
#[derive(Clone, Copy, Debug)]
pub struct FrameControl {
/// Sequence number of the animation chunk, starting from 0
pub sequence_number: u32,
/// Width of the following frame
pub width: u32,
/// Height of the following frame
pub height: u32,
/// X position at which to render the following frame
pub x_offset: u32,
/// Y position at which to render the following frame
pub y_offset: u32,
/// Frame delay fraction numerator
pub delay_num: u16,
/// Frame delay fraction denominator
pub delay_den: u16,
/// Type of frame area disposal to be done after rendering this frame
pub dispose_op: DisposeOp,
/// Type of frame area rendering for this frame
pub blend_op: BlendOp,
}
impl Default for FrameControl {
fn default() -> FrameControl {
FrameControl {
sequence_number: 0,
width: 0,
height: 0,
x_offset: 0,
y_offset: 0,
delay_num: 1,
delay_den: 30,
dispose_op: DisposeOp::None,
blend_op: BlendOp::Source,
}
}
}
impl FrameControl {
pub fn set_seq_num(&mut self, s: u32) {
self.sequence_number = s;
}
pub fn inc_seq_num(&mut self, i: u32) {
self.sequence_number += i;
}
pub fn encode<W: Write>(self, w: &mut W) -> encoder::Result<()> {
let mut data = [0u8; 26];
data[..4].copy_from_slice(&self.sequence_number.to_be_bytes());
data[4..8].copy_from_slice(&self.width.to_be_bytes());
data[8..12].copy_from_slice(&self.height.to_be_bytes());
data[12..16].copy_from_slice(&self.x_offset.to_be_bytes());
data[16..20].copy_from_slice(&self.y_offset.to_be_bytes());
data[20..22].copy_from_slice(&self.delay_num.to_be_bytes());
data[22..24].copy_from_slice(&self.delay_den.to_be_bytes());
data[24] = self.dispose_op as u8;
data[25] = self.blend_op as u8;
encoder::write_chunk(w, chunk::fcTL, &data)
}
}
/// Animation control information
#[derive(Clone, Copy, Debug)]
pub struct AnimationControl {
/// Number of frames
pub num_frames: u32,
/// Number of times to loop this APNG. 0 indicates infinite looping.
pub num_plays: u32,
}
impl AnimationControl {
pub fn encode<W: Write>(self, w: &mut W) -> encoder::Result<()> {
let mut data = [0; 8];
data[..4].copy_from_slice(&self.num_frames.to_be_bytes());
data[4..].copy_from_slice(&self.num_plays.to_be_bytes());
encoder::write_chunk(w, chunk::acTL, &data)
}
}
/// The type and strength of applied compression.
#[derive(Debug, Clone, Copy)]
pub enum Compression {
/// Default level
Default,
/// Fast minimal compression
Fast,
/// Higher compression level
///
/// Best in this context isn't actually the highest possible level
/// the encoder can do, but is meant to emulate the `Best` setting in the `Flate2`
/// library.
Best,
#[deprecated(
since = "0.17.6",
note = "use one of the other compression levels instead, such as 'fast'"
)]
Huffman,
#[deprecated(
since = "0.17.6",
note = "use one of the other compression levels instead, such as 'fast'"
)]
Rle,
}
impl Default for Compression {
fn default() -> Self {
Self::Default
}
}
/// An unsigned integer scaled version of a floating point value,
/// equivalent to an integer quotient with fixed denominator (100_000)).
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct ScaledFloat(u32);
impl ScaledFloat {
const SCALING: f32 = 100_000.0;
/// Gets whether the value is within the clamped range of this type.
pub fn in_range(value: f32) -> bool {
value >= 0.0 && (value * Self::SCALING).floor() <= std::u32::MAX as f32
}
/// Gets whether the value can be exactly converted in round-trip.
#[allow(clippy::float_cmp)] // Stupid tool, the exact float compare is _the entire point_.
pub fn exact(value: f32) -> bool {
let there = Self::forward(value);
let back = Self::reverse(there);
value == back
}
fn forward(value: f32) -> u32 {
(value.max(0.0) * Self::SCALING).floor() as u32
}
fn reverse(encoded: u32) -> f32 {
encoded as f32 / Self::SCALING
}
/// Slightly inaccurate scaling and quantization.
/// Clamps the value into the representable range if it is negative or too large.
pub fn new(value: f32) -> Self {
Self(Self::forward(value))
}
/// Fully accurate construction from a value scaled as per specification.
pub fn from_scaled(val: u32) -> Self {
Self(val)
}
/// Get the accurate encoded value.
pub fn into_scaled(self) -> u32 {
self.0
}
/// Get the unscaled value as a floating point.
pub fn into_value(self) -> f32 {
Self::reverse(self.0)
}
pub(crate) fn encode_gama<W: Write>(self, w: &mut W) -> encoder::Result<()> {
encoder::write_chunk(w, chunk::gAMA, &self.into_scaled().to_be_bytes())
}
}
/// Chromaticities of the color space primaries
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct SourceChromaticities {
pub white: (ScaledFloat, ScaledFloat),
pub red: (ScaledFloat, ScaledFloat),
pub green: (ScaledFloat, ScaledFloat),
pub blue: (ScaledFloat, ScaledFloat),
}
impl SourceChromaticities {
pub fn new(white: (f32, f32), red: (f32, f32), green: (f32, f32), blue: (f32, f32)) -> Self {
SourceChromaticities {
white: (ScaledFloat::new(white.0), ScaledFloat::new(white.1)),
red: (ScaledFloat::new(red.0), ScaledFloat::new(red.1)),
green: (ScaledFloat::new(green.0), ScaledFloat::new(green.1)),
blue: (ScaledFloat::new(blue.0), ScaledFloat::new(blue.1)),
}
}
#[rustfmt::skip]
pub fn to_be_bytes(self) -> [u8; 32] {
let white_x = self.white.0.into_scaled().to_be_bytes();
let white_y = self.white.1.into_scaled().to_be_bytes();
let red_x = self.red.0.into_scaled().to_be_bytes();
let red_y = self.red.1.into_scaled().to_be_bytes();
let green_x = self.green.0.into_scaled().to_be_bytes();
let green_y = self.green.1.into_scaled().to_be_bytes();
let blue_x = self.blue.0.into_scaled().to_be_bytes();
let blue_y = self.blue.1.into_scaled().to_be_bytes();
[
white_x[0], white_x[1], white_x[2], white_x[3],
white_y[0], white_y[1], white_y[2], white_y[3],
red_x[0], red_x[1], red_x[2], red_x[3],
red_y[0], red_y[1], red_y[2], red_y[3],
green_x[0], green_x[1], green_x[2], green_x[3],
green_y[0], green_y[1], green_y[2], green_y[3],
blue_x[0], blue_x[1], blue_x[2], blue_x[3],
blue_y[0], blue_y[1], blue_y[2], blue_y[3],
]
}
pub fn encode<W: Write>(self, w: &mut W) -> encoder::Result<()> {
encoder::write_chunk(w, chunk::cHRM, &self.to_be_bytes())
}
}
/// The rendering intent for an sRGB image.
///
/// Presence of this data also indicates that the image conforms to the sRGB color space.
#[repr(u8)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum SrgbRenderingIntent {
/// For images preferring good adaptation to the output device gamut at the expense of colorimetric accuracy, such as photographs.
Perceptual = 0,
/// For images requiring colour appearance matching (relative to the output device white point), such as logos.
RelativeColorimetric = 1,
/// For images preferring preservation of saturation at the expense of hue and lightness, such as charts and graphs.
Saturation = 2,
/// For images requiring preservation of absolute colorimetry, such as previews of images destined for a different output device (proofs).
AbsoluteColorimetric = 3,
}
impl SrgbRenderingIntent {
pub(crate) fn into_raw(self) -> u8 {
self as u8
}
pub(crate) fn from_raw(raw: u8) -> Option<Self> {
match raw {
0 => Some(SrgbRenderingIntent::Perceptual),
1 => Some(SrgbRenderingIntent::RelativeColorimetric),
2 => Some(SrgbRenderingIntent::Saturation),
3 => Some(SrgbRenderingIntent::AbsoluteColorimetric),
_ => None,
}
}
pub fn encode<W: Write>(self, w: &mut W) -> encoder::Result<()> {
encoder::write_chunk(w, chunk::sRGB, &[self.into_raw()])
}
}
/// PNG info struct
#[derive(Clone, Debug)]
#[non_exhaustive]
pub struct Info<'a> {
pub width: u32,
pub height: u32,
pub bit_depth: BitDepth,
/// How colors are stored in the image.
pub color_type: ColorType,
pub interlaced: bool,
/// The image's `tRNS` chunk, if present; contains the alpha channel of the image's palette, 1 byte per entry.
pub trns: Option<Cow<'a, [u8]>>,
pub pixel_dims: Option<PixelDimensions>,
/// The image's `PLTE` chunk, if present; contains the RGB channels (in that order) of the image's palettes, 3 bytes per entry (1 per channel).
pub palette: Option<Cow<'a, [u8]>>,
/// The contents of the image's gAMA chunk, if present.
/// Prefer `source_gamma` to also get the derived replacement gamma from sRGB chunks.
pub gama_chunk: Option<ScaledFloat>,
/// The contents of the image's `cHRM` chunk, if present.
/// Prefer `source_chromaticities` to also get the derived replacements from sRGB chunks.
pub chrm_chunk: Option<SourceChromaticities>,
pub frame_control: Option<FrameControl>,
pub animation_control: Option<AnimationControl>,
pub compression: Compression,
/// Gamma of the source system.
/// Set by both `gAMA` as well as to a replacement by `sRGB` chunk.
pub source_gamma: Option<ScaledFloat>,
/// Chromaticities of the source system.
/// Set by both `cHRM` as well as to a replacement by `sRGB` chunk.
pub source_chromaticities: Option<SourceChromaticities>,
/// The rendering intent of an SRGB image.
///
/// Presence of this value also indicates that the image conforms to the SRGB color space.
pub srgb: Option<SrgbRenderingIntent>,
/// The ICC profile for the image.
pub icc_profile: Option<Cow<'a, [u8]>>,
/// tEXt field
pub uncompressed_latin1_text: Vec<TEXtChunk>,
/// zTXt field
pub compressed_latin1_text: Vec<ZTXtChunk>,
/// iTXt field
pub utf8_text: Vec<ITXtChunk>,
}
impl Default for Info<'_> {
fn default() -> Info<'static> {
Info {
width: 0,
height: 0,
bit_depth: BitDepth::Eight,
color_type: ColorType::Grayscale,
interlaced: false,
palette: None,
trns: None,
gama_chunk: None,
chrm_chunk: None,
pixel_dims: None,
frame_control: None,
animation_control: None,
// Default to `deflate::Compression::Fast` and `filter::FilterType::Sub`
// to maintain backward compatible output.
compression: Compression::Fast,
source_gamma: None,
source_chromaticities: None,
srgb: None,
icc_profile: None,
uncompressed_latin1_text: Vec::new(),
compressed_latin1_text: Vec::new(),
utf8_text: Vec::new(),
}
}
}
impl Info<'_> {
/// A utility constructor for a default info with width and height.
pub fn with_size(width: u32, height: u32) -> Self {
Info {
width,
height,
..Default::default()
}
}
/// Size of the image, width then height.
pub fn size(&self) -> (u32, u32) {
(self.width, self.height)
}
/// Returns true if the image is an APNG image.
pub fn is_animated(&self) -> bool {
self.frame_control.is_some() && self.animation_control.is_some()
}
/// Returns the frame control information of the image.
pub fn animation_control(&self) -> Option<&AnimationControl> {
self.animation_control.as_ref()
}
/// Returns the frame control information of the current frame
pub fn frame_control(&self) -> Option<&FrameControl> {
self.frame_control.as_ref()
}
/// Returns the number of bits per pixel.
pub fn bits_per_pixel(&self) -> usize {
self.color_type.samples() * self.bit_depth as usize
}
/// Returns the number of bytes per pixel.
pub fn bytes_per_pixel(&self) -> usize {
// If adjusting this for expansion or other transformation passes, remember to keep the old
// implementation for bpp_in_prediction, which is internal to the png specification.
self.color_type.samples() * ((self.bit_depth as usize + 7) >> 3)
}
/// Return the number of bytes for this pixel used in prediction.
///
/// Some filters use prediction, over the raw bytes of a scanline. Where a previous pixel is
/// require for such forms the specification instead references previous bytes. That is, for
/// a gray pixel of bit depth 2, the pixel used in prediction is actually 4 pixels prior. This
/// has the consequence that the number of possible values is rather small. To make this fact
/// more obvious in the type system and the optimizer we use an explicit enum here.
pub(crate) fn bpp_in_prediction(&self) -> BytesPerPixel {
BytesPerPixel::from_usize(self.bytes_per_pixel())
}
/// Returns the number of bytes needed for one deinterlaced image.
pub fn raw_bytes(&self) -> usize {
self.height as usize * self.raw_row_length()
}
/// Returns the number of bytes needed for one deinterlaced row.
pub fn raw_row_length(&self) -> usize {
self.raw_row_length_from_width(self.width)
}
pub(crate) fn checked_raw_row_length(&self) -> Option<usize> {
self.color_type
.checked_raw_row_length(self.bit_depth, self.width)
}
/// Returns the number of bytes needed for one deinterlaced row of width `width`.
pub fn raw_row_length_from_width(&self, width: u32) -> usize {
self.color_type
.raw_row_length_from_width(self.bit_depth, width)
}
/// Encode this header to the writer.
///
/// Note that this does _not_ include the PNG signature, it starts with the IHDR chunk and then
/// includes other chunks that were added to the header.
pub fn encode<W: Write>(&self, mut w: W) -> encoder::Result<()> {
// Encode the IHDR chunk
let mut data = [0; 13];
data[..4].copy_from_slice(&self.width.to_be_bytes());
data[4..8].copy_from_slice(&self.height.to_be_bytes());
data[8] = self.bit_depth as u8;
data[9] = self.color_type as u8;
data[12] = self.interlaced as u8;
encoder::write_chunk(&mut w, chunk::IHDR, &data)?;
// Encode the pHYs chunk
if let Some(pd) = self.pixel_dims {
let mut phys_data = [0; 9];
phys_data[0..4].copy_from_slice(&pd.xppu.to_be_bytes());
phys_data[4..8].copy_from_slice(&pd.yppu.to_be_bytes());
match pd.unit {
Unit::Meter => phys_data[8] = 1,
Unit::Unspecified => phys_data[8] = 0,
}
encoder::write_chunk(&mut w, chunk::pHYs, &phys_data)?;
}
if let Some(p) = &self.palette {
encoder::write_chunk(&mut w, chunk::PLTE, p)?;
};
if let Some(t) = &self.trns {
encoder::write_chunk(&mut w, chunk::tRNS, t)?;
}
// If specified, the sRGB information overrides the source gamma and chromaticities.
if let Some(srgb) = &self.srgb {
let gamma = crate::srgb::substitute_gamma();
let chromaticities = crate::srgb::substitute_chromaticities();
srgb.encode(&mut w)?;
gamma.encode_gama(&mut w)?;
chromaticities.encode(&mut w)?;
} else {
if let Some(gma) = self.source_gamma {
gma.encode_gama(&mut w)?
}
if let Some(chrms) = self.source_chromaticities {
chrms.encode(&mut w)?;
}
}
if let Some(actl) = self.animation_control {
actl.encode(&mut w)?;
}
for text_chunk in &self.uncompressed_latin1_text {
text_chunk.encode(&mut w)?;
}
for text_chunk in &self.compressed_latin1_text {
text_chunk.encode(&mut w)?;
}
for text_chunk in &self.utf8_text {
text_chunk.encode(&mut w)?;
}
Ok(())
}
}
impl BytesPerPixel {
pub(crate) fn from_usize(bpp: usize) -> Self {
match bpp {
1 => BytesPerPixel::One,
2 => BytesPerPixel::Two,
3 => BytesPerPixel::Three,
4 => BytesPerPixel::Four,
6 => BytesPerPixel::Six, // Only rgb×16bit
8 => BytesPerPixel::Eight, // Only rgba×16bit
_ => unreachable!("Not a possible byte rounded pixel width"),
}
}
pub(crate) fn into_usize(self) -> usize {
self as usize
}
}
bitflags! {
/// Output transformations
///
/// Many flags from libpng are not yet supported. A PR discussing/adding them would be nice.
///
#[doc = "
```c
/// Discard the alpha channel
const STRIP_ALPHA = 0x0002; // read only
/// Expand 1; 2 and 4-bit samples to bytes
const PACKING = 0x0004; // read and write
/// Change order of packed pixels to LSB first
const PACKSWAP = 0x0008; // read and write
/// Invert monochrome images
const INVERT_MONO = 0x0020; // read and write
/// Normalize pixels to the sBIT depth
const SHIFT = 0x0040; // read and write
/// Flip RGB to BGR; RGBA to BGRA
const BGR = 0x0080; // read and write
/// Flip RGBA to ARGB or GA to AG
const SWAP_ALPHA = 0x0100; // read and write
/// Byte-swap 16-bit samples
const SWAP_ENDIAN = 0x0200; // read and write
/// Change alpha from opacity to transparency
const INVERT_ALPHA = 0x0400; // read and write
const STRIP_FILLER = 0x0800; // write only
const STRIP_FILLER_BEFORE = 0x0800; // write only
const STRIP_FILLER_AFTER = 0x1000; // write only
const GRAY_TO_RGB = 0x2000; // read only
const EXPAND_16 = 0x4000; // read only
/// Similar to STRIP_16 but in libpng considering gamma?
/// Not entirely sure the documentation says it is more
/// accurate but doesn't say precisely how.
const SCALE_16 = 0x8000; // read only
```
"]
pub struct Transformations: u32 {
/// No transformation
const IDENTITY = 0x00000; // read and write */
/// Strip 16-bit samples to 8 bits
const STRIP_16 = 0x00001; // read only */
/// Expand paletted images to RGB; expand grayscale images of
/// less than 8-bit depth to 8-bit depth; and expand tRNS chunks
/// to alpha channels.
const EXPAND = 0x00010; // read only */
/// Expand paletted images to include an alpha channel. Implies `EXPAND`.
const ALPHA = 0x10000; // read only */
}
}
impl Transformations {
/// Transform every input to 8bit grayscale or color.
///
/// This sets `EXPAND` and `STRIP_16` which is similar to the default transformation used by
/// this library prior to `0.17`.
pub fn normalize_to_color8() -> Transformations {
Transformations::EXPAND | Transformations::STRIP_16
}
}
/// Instantiate the default transformations, the identity transform.
impl Default for Transformations {
fn default() -> Transformations {
Transformations::IDENTITY
}
}
#[derive(Debug)]
pub struct ParameterError {
inner: ParameterErrorKind,
}
#[derive(Debug)]
pub(crate) enum ParameterErrorKind {
/// A provided buffer must be have the exact size to hold the image data. Where the buffer can
/// be allocated by the caller, they must ensure that it has a minimum size as hinted previously.
/// Even though the size is calculated from image data, this does counts as a parameter error
/// because they must react to a value produced by this library, which can have been subjected
/// to limits.
ImageBufferSize { expected: usize, actual: usize },
/// A bit like return `None` from an iterator.
/// We use it to differentiate between failing to seek to the next image in a sequence and the
/// absence of a next image. This is an error of the caller because they should have checked
/// the number of images by inspecting the header data returned when opening the image. This
/// library will perform the checks necessary to ensure that data was accurate or error with a
/// format error otherwise.
PolledAfterEndOfImage,
}
impl From<ParameterErrorKind> for ParameterError {
fn from(inner: ParameterErrorKind) -> Self {
ParameterError { inner }
}
}
impl fmt::Display for ParameterError {
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
use ParameterErrorKind::*;
match self.inner {
ImageBufferSize { expected, actual } => {
write!(fmt, "wrong data size, expected {} got {}", expected, actual)
}
PolledAfterEndOfImage => write!(fmt, "End of image has been reached"),
}
}
}
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