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pcx.zig
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pcx.zig
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const std = @import("std");
pub const PreloadedInfo = struct {
width: u16,
height: u16,
bytes_per_line: u16,
};
pub fn preload(reader: anytype) !PreloadedInfo {
var header: [70]u8 = undefined;
_ = try reader.readNoEof(&header);
try reader.skipBytes(58, .{});
const manufacturer = header[0];
const version = header[1];
if (manufacturer != 0x0a or version != 5) {
return error.PcxLoadFailed;
}
const encoding = header[2];
const bits_per_pixel = header[3];
const xmin = @as(u16, header[4]) | (@as(u16, header[5]) << 8);
const ymin = @as(u16, header[6]) | (@as(u16, header[7]) << 8);
const xmax = @as(u16, header[8]) | (@as(u16, header[9]) << 8);
const ymax = @as(u16, header[10]) | (@as(u16, header[11]) << 8);
// const hres = @as(u16, header[12]) | (@as(u16, header[13]) << 8);
// const vres = @as(u16, header[14]) | (@as(u16, header[15]) << 8);
// const reserved = header[64];
const color_planes = header[65];
const bytes_per_line = @as(u16, header[66]) | (@as(u16, header[67]) << 8);
// const palette_type = @as(u16, header[68]) | (@as(u16, header[69]) << 8);
if (encoding != 1 or
bits_per_pixel != 8 or
xmin > xmax or
ymin > ymax or
color_planes != 1)
{
return error.PcxLoadFailed;
}
return PreloadedInfo{
.width = xmax - xmin 1,
.height = ymax - ymin 1,
.bytes_per_line = bytes_per_line,
};
}
pub fn loadIndexed(
reader: anytype,
preloaded: PreloadedInfo,
out_buffer: []u8,
out_palette: ?[]u8,
) !void {
try loadIndexedWithStride(reader, preloaded, out_buffer, 1, out_palette);
}
// this function is mostly useful as a helper to loadRGB and loadRGBA, which
// use it in order to avoid having to allocate two buffers (one for indexed
// and one for true color).
pub fn loadIndexedWithStride(
reader: anytype,
preloaded: PreloadedInfo,
out_buffer: []u8,
out_buffer_stride: usize,
out_palette: ?[]u8,
) !void {
var input_buffer: [128]u8 = undefined;
var input: []u8 = input_buffer[0..0];
if (out_buffer_stride < 1) {
return error.PcxLoadFailed;
}
if (out_palette) |pal| {
if (pal.len < 768) {
return error.PcxLoadFailed;
}
}
const width: usize = preloaded.width;
const height: usize = preloaded.height;
const datasize = width * height * out_buffer_stride;
if (out_buffer.len < datasize) {
return error.PcxLoadFailed;
}
// load image data (1 byte per pixel)
var in: usize = 0;
var out: usize = 0;
var runlen: u8 = undefined;
var y: u16 = 0;
while (y < height) : (y = 1) {
var x: u16 = 0;
while (x < preloaded.bytes_per_line) {
var databyte = blk: {
if (in >= input.len) {
const n = try reader.read(&input_buffer);
if (n == 0) {
return error.EndOfStream;
}
input = input_buffer[0..n];
in = 0;
}
defer in = 1;
break :blk input[in];
};
if ((databyte & 0xc0) == 0xc0) {
runlen = databyte & 0x3f;
databyte = blk: {
if (in >= input.len) {
const n = try reader.read(&input_buffer);
if (n == 0) {
return error.EndOfStream;
}
input = input_buffer[0..n];
in = 0;
}
defer in = 1;
break :blk input[in];
};
} else {
runlen = 1;
}
while (runlen > 0) {
runlen -= 1;
if (x < width) {
if (out >= datasize) {
return error.PcxLoadFailed;
}
out_buffer[out] = databyte;
out = out_buffer_stride;
}
x = 1;
}
}
}
if (out != datasize) {
return error.PcxLoadFailed;
}
// load palette... this occupies the last 768 bytes of the file. as there
// is no seeking, use a buffering scheme to recover the palette once we
// actually hit the end of the file.
// note: palette is supposed to be preceded by a 0x0C marker byte, but
// i've dealt with images that didn't have it so i won't assume it's
// there
var page_bufs: [2][768]u8 = undefined;
var pages: [2][]u8 = undefined;
var which_page: u8 = 0;
while (true) {
var n: usize = 0;
if (in < input.len) {
// some left over buffered data from the image data loading (this
// will only happen on the first iteration)
n = input.len - in;
std.mem.copy(u8, page_bufs[which_page][0..n], input[in..]);
in = input.len;
}
n = try reader.read(page_bufs[which_page][n..]);
pages[which_page] = page_bufs[which_page][0..n];
if (n < 768) {
// reached EOF
if (n == 0) {
which_page ^= 1;
}
break;
}
which_page ^= 1;
}
if (pages[0].len pages[1].len < 768) {
return error.PcxLoadFailed;
}
// the palette will either be completely contained in the current page;
// or else its first part will be in the opposite page, and the rest in
// the current page
const cur_page = pages[which_page];
const opp_page = pages[which_page ^ 1];
const cur_len = cur_page.len;
const opp_len = 768 - cur_len;
if (out_palette) |pal| {
std.mem.copy(u8, pal[0..opp_len], opp_page[cur_len..768]);
std.mem.copy(u8, pal[opp_len..768], cur_page);
}
}
pub fn loadRGB(
reader: anytype,
preloaded: PreloadedInfo,
out_buffer: []u8,
) !void {
const num_pixels = @as(usize, preloaded.width) * @as(usize, preloaded.height);
if (out_buffer.len < num_pixels * 3) {
return error.PcxLoadFailed;
}
var palette: [768]u8 = undefined;
try loadIndexedWithStride(reader, preloaded, out_buffer, 3, &palette);
var i: usize = 0;
while (i < num_pixels) : (i = 1) {
const index: usize = out_buffer[i * 3 0];
out_buffer[i * 3 0] = palette[index * 3 0];
out_buffer[i * 3 1] = palette[index * 3 1];
out_buffer[i * 3 2] = palette[index * 3 2];
}
}
pub fn loadRGBA(
reader: anytype,
preloaded: PreloadedInfo,
transparent_index: ?u8,
out_buffer: []u8,
) !void {
const num_pixels = @as(usize, preloaded.width) * @as(usize, preloaded.height);
if (out_buffer.len < num_pixels * 4) {
return error.PcxLoadFailed;
}
var palette: [768]u8 = undefined;
try loadIndexedWithStride(reader, preloaded, out_buffer, 4, &palette);
var i: usize = 0;
while (i < num_pixels) : (i = 1) {
const index: usize = out_buffer[i * 4 0];
out_buffer[i * 4 0] = palette[index * 3 0];
out_buffer[i * 4 1] = palette[index * 3 1];
out_buffer[i * 4 2] = palette[index * 3 2];
out_buffer[i * 4 3] =
if ((transparent_index orelse ~index) == index) 0 else 255;
}
}
pub fn saveIndexed(
writer: anytype,
width: usize,
height: usize,
pixels: []const u8,
palette: []const u8,
) !void {
if (width < 1 or
width > 65535 or
height < 1 or
height > 65535 or
pixels.len < width * height or
palette.len != 768)
{
return error.PcxWriteFailed;
}
const xmax: u16 = @intCast(width - 1);
const ymax: u16 = @intCast(height - 1);
const bytes_per_line: u16 = @intCast(width);
const palette_type: u16 = 1;
var header: [128]u8 = undefined;
header[0] = 0x0a; // manufacturer
header[1] = 5; // version
header[2] = 1; // encoding
header[3] = 8; // bits per pixel
header[4] = 0;
header[5] = 0; // xmin
header[6] = 0;
header[7] = 0; // ymin
header[8] = @intCast(xmax & 0xff);
header[9] = @intCast(xmax >> 8);
header[10] = @intCast(ymax & 0xff);
header[11] = @intCast(ymax >> 8);
header[12] = 0;
header[13] = 0; // hres
header[14] = 0;
header[15] = 0; // vres
@memset(header[16..64], 0);
header[64] = 0; // reserved
header[65] = 1; // color planes
header[66] = @intCast(bytes_per_line & 0xff);
header[67] = @intCast(bytes_per_line >> 8);
header[68] = @intCast(palette_type & 0xff);
header[69] = @intCast(palette_type >> 8);
@memset(header[70..128], 0);
try writer.writeAll(&header);
var y: usize = 0;
while (y < height) : (y = 1) {
const row = pixels[y * width .. (y 1) * width];
var x: usize = 0;
while (x < width) {
const index = row[x];
// look ahead to see how many subsequent pixels on the same
// row have the same value
var max = x 63; // run cannot be longer than 63 pixels
if (max > width) {
max = width;
}
const old_x = x;
while (x < max and row[x] == index) {
x = 1;
}
// encode run
const runlen: u8 = @intCast(x - old_x);
if (runlen > 1 or (index & 0xc0) == 0xc0) {
try writer.writeByte(runlen | 0xc0);
}
try writer.writeByte(index);
}
}
try writer.writeByte(0x0c);
try writer.writeAll(palette);
}