#include "imageexport.h"
#include "log.h"
#include <QFile>
// CRC code from: http://www.libpng.org/pub/png/spec/1.2/PNG-CRCAppendix.html
/* Table of CRCs of all 8-bit messages. */
unsigned long crc_table[256];
/* Flag: has the table been computed? Initially false. */
int crc_table_computed = 0;
/* Make the table for a fast CRC. */
void make_crc_table(void)
{
unsigned long c;
int n, k;
for (n = 0; n < 256; n++) {
c = (unsigned long) n;
for (k = 0; k < 8; k++) {
if (c & 1)
c = 0xedb88320L ^ (c >> 1);
else
c = c >> 1;
}
crc_table[n] = c;
}
crc_table_computed = 1;
}
/* Update a running CRC with the bytes buf[0..len-1]--the CRC
should be initialized to all 1's, and the transmitted value
is the 1's complement of the final running CRC (see the
crc() routine below)). */
unsigned long update_crc(unsigned long crc, QByteArray buf,
int len)
{
unsigned long c = crc;
int n;
if (!crc_table_computed)
make_crc_table();
for (n = 0; n < len; n++) {
c = crc_table[(c ^ static_cast<unsigned char>(buf[n])) & 0xff] ^ (c >> 8);
}
return c;
}
/* Return the CRC of the bytes buf[0..len-1]. */
unsigned long crc(QByteArray buf, int len)
{
return update_crc(0xffffffffL, buf, len) ^ 0xffffffffL;
}
// Qt does not have the ability to export indexed PNG files with a
// bit depth of 4--it only supports 8. This can cause problems with
// some image editing programs because they will revert the bit depth,
// and re-importing into porymap (Qt), will cause the image to be
// interpreted as having too many colors. By properly exporting 16-palette
// images in porymap, we can effectively avoid that issue.
void exportIndexed4BPPPng(QImage image, QString filepath)
{
// Verify that the image is not empty
if (image.isNull()) {
logError(QString("Failed to export %1: the image is null.").arg(filepath));
return;
}
// Header
QByteArray pngHeader;
pngHeader.append(static_cast<char>(0x89));
pngHeader.append("PNG");
pngHeader.append(static_cast<char>(0x0D));
pngHeader.append(static_cast<char>(0x0A));
pngHeader.append(static_cast<char>(0x1A));
pngHeader.append(static_cast<char>(0x0A));
// IHDR Chunk
QByteArray ihdr;
ihdr.append("IHDR");
int width = image.width();
ihdr.append(static_cast<char>((width >> 24) & 0xFF));
ihdr.append(static_cast<char>((width >> 16) & 0xFF));
ihdr.append(static_cast<char>((width >> 8) & 0xFF));
ihdr.append(static_cast<char>((width >> 0) & 0xFF));
int height = image.height();
ihdr.append(static_cast<char>((height >> 24) & 0xFF));
ihdr.append(static_cast<char>((height >> 16) & 0xFF));
ihdr.append(static_cast<char>((height >> 8) & 0xFF));
ihdr.append(static_cast<char>((height >> 0) & 0xFF));
ihdr.append(static_cast<char>(4)); // bit depth
ihdr.append(static_cast<char>(3)); // indexed color type
ihdr.append(static_cast<char>(0)); // compression method
ihdr.append(static_cast<char>(0)); // filter method
ihdr.append(static_cast<char>(0)); // interlace method
unsigned long ihdrCRC = crc(ihdr, 17);
ihdr.append(static_cast<char>((ihdrCRC >> 24) & 0xFF));
ihdr.append(static_cast<char>((ihdrCRC >> 16) & 0xFF));
ihdr.append(static_cast<char>((ihdrCRC >> 8) & 0xFF));
ihdr.append(static_cast<char>((ihdrCRC >> 0) & 0xFF));
// PLTE Chunk
int numColors = image.colorCount();
QByteArray plte;
plte.append("PLTE");
for (int i = 0; i < numColors; i++) {
QRgb rgb = image.colorTable().at(i);
plte.append(static_cast<char>(qRed(rgb)));
plte.append(static_cast<char>(qGreen(rgb)));
plte.append(static_cast<char>(qBlue(rgb)));
}
unsigned long plteCRC = crc(plte, numColors * 3 + 4);
plte.append(static_cast<char>((plteCRC >> 24) & 0xFF));
plte.append(static_cast<char>((plteCRC >> 16) & 0xFF));
plte.append(static_cast<char>((plteCRC >> 8) & 0xFF));
plte.append(static_cast<char>((plteCRC >> 0) & 0xFF));
// IDAT Chunk
QByteArray idat;
idat.append("IDAT");
unsigned long count = 0;
char val = 0;
QByteArray pixelData;
for (int y = 0; y < image.height(); y++) {
pixelData.append(static_cast<char>(0));
for (int x = 0; x < image.width(); x++) {
int colorId = image.pixelIndex(x, y);
if (count % 2 == 0) {
val = static_cast<char>(val & 0x0F) | static_cast<char>(colorId << 4);
} else {
val = static_cast<char>(val & 0xF0) | (static_cast<char>(colorId));
pixelData.append(val);
}
count++;
}
}
QByteArray compressedPixelData = qCompress(pixelData);
// Qt's qCompress/qDecompress use a pointless 4-byte header, even though
// they are using DEFLATE under the hood. If we strip the 4-byte header,
// it's perfectly compatible with the PNG compression spec.
compressedPixelData.remove(0, 4);
idat.append(compressedPixelData);
unsigned long idatCRC = crc(idat, compressedPixelData.length() + 4);
idat.append(static_cast<char>((idatCRC >> 24) & 0xFF));
idat.append(static_cast<char>((idatCRC >> 16) & 0xFF));
idat.append(static_cast<char>((idatCRC >> 8) & 0xFF));
idat.append(static_cast<char>((idatCRC >> 0) & 0xFF));
// IEND Chunk
QByteArray iend;
iend.append("IEND");
unsigned long iendCRC = crc(iend, 4);
iend.append(static_cast<char>((iendCRC >> 24) & 0xFF));
iend.append(static_cast<char>((iendCRC >> 16) & 0xFF));
iend.append(static_cast<char>((iendCRC >> 8) & 0xFF));
iend.append(static_cast<char>((iendCRC >> 0) & 0xFF));
QByteArray data;
data.append(pngHeader);
data.append(static_cast<char>(((ihdr.length() - 8) >> 24) & 0xFF));
data.append(static_cast<char>(((ihdr.length() - 8) >> 16) & 0xFF));
data.append(static_cast<char>(((ihdr.length() - 8) >> 8) & 0xFF));
data.append(static_cast<char>(((ihdr.length() - 8) >> 0) & 0xFF));
data.append(ihdr);
data.append(static_cast<char>(((plte.length() - 8) >> 24) & 0xFF));
data.append(static_cast<char>(((plte.length() - 8) >> 16) & 0xFF));
data.append(static_cast<char>(((plte.length() - 8) >> 8) & 0xFF));
data.append(static_cast<char>(((plte.length() - 8) >> 0) & 0xFF));
data.append(plte);
data.append(static_cast<char>(((idat.length() - 8) >> 24) & 0xFF));
data.append(static_cast<char>(((idat.length() - 8) >> 16) & 0xFF));
data.append(static_cast<char>(((idat.length() - 8) >> 8) & 0xFF));
data.append(static_cast<char>(((idat.length() - 8) >> 0) & 0xFF));
data.append(idat);
data.append(static_cast<char>(((iend.length() - 8) >> 24) & 0xFF));
data.append(static_cast<char>(((iend.length() - 8) >> 16) & 0xFF));
data.append(static_cast<char>(((iend.length() - 8) >> 8) & 0xFF));
data.append(static_cast<char>(((iend.length() - 8) >> 0) & 0xFF));
data.append(iend);
QFile file(filepath);
if (!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
logError(QString("Could not save '%1'. ").arg(filepath) + file.errorString());
return;
}
file.write(data);
file.close();
}