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use errors;
use io;
use memio;
// A decoded PNG image.
export type image = struct {
// Image header
ihdr: ihdr,
// RGBA palette data (if present, otherwise an empty slice)
palette: []u32,
// Raw pixel data
pixels: []u8,
};
// Reads a PNG image from an [[io::handle]], returning the decoded header,
// palette (if present), and raw pixel data. The caller must pass the return
// value to [[image_finish]] to discard resources associated with the image.
export fn load(in: io::handle) (image | error) = {
let success = false;
const reader = newreader(in)?;
match (nextchunk(&reader)?) {
case io::EOF =>
return invalid;
case let ctype: u32 =>
if (ctype != IHDR) {
return invalid;
};
};
const ihdr = ihdr_read(&reader)?;
let pixels: ([]u8 | void) = void;
defer if (!success && pixels is []u8) free(pixels as []u8);
let palette: []u32 = [];
defer if (!success) free(palette);
for (true) match (nextchunk(&reader)?) {
case io::EOF =>
return invalid;
case let ctype: u32 =>
switch (ctype) {
case IHDR =>
return invalid;
case PLTE =>
if (len(palette) != 0) {
return invalid;
};
let plte = new_plte_reader(&reader)?;
palette = alloc([0...], plte_ncolors(&plte));
plte_read(&plte, palette)?;
case IDAT =>
if (pixels is []u8) {
return invalid;
};
let pixbuf: []u8 = alloc([0...], decoder_bufsiz(&ihdr));
defer free(pixbuf);
let idat = new_idat_reader(&reader);
let dec = newdecoder(&idat, &ihdr, pixbuf)?;
defer io::close(&dec)!;
pixels = io::drain(&dec)?;
case IEND =>
iend_read(&reader)?;
break;
case =>
if (is_critical(ctype)) {
return unsupported;
};
io::copy(io::empty, &reader)?;
};
};
if (pixels is void) {
return invalid;
};
success = true;
return image {
ihdr = ihdr,
palette = palette,
pixels = pixels as []u8,
};
};
// Frees resources associated with an [[image]].
export fn image_finish(img: *image) void = {
free(img.palette);
free(img.pixels);
};
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