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