Use libpng for writing row by row

CMakeLists.txt

@@ -6,6 +6,7 @@ set(CMAKE_AUTOMOC ON)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 find_package(Qt6 6.2 REQUIRED COMPONENTS Quick QuickControls2)
+find_package(PNG REQUIRED)
 
 
 qt_add_executable(apptexcrafting
@@ -19,6 +20,7 @@ qt_add_qml_module(apptexcrafting
         Main.qml
         TexSlot.qml
         SOURCES texturecrafter.h texturecrafter.cpp
+        RESOURCES
 )
 
 # Qt for iOS sets MACOSX_BUNDLE_GUI_IDENTIFIER automatically since Qt 6.1.
@@ -34,6 +36,7 @@ set_target_properties(apptexcrafting PROPERTIES
 
 target_link_libraries(apptexcrafting
     PRIVATE Qt6::Quick
+    PNG::PNG
 )
 
 include(GNUInstallDirs)

Main.qml

@@ -8,7 +8,7 @@ ApplicationWindow {
     width: 640
     height: 480
     visible: true
-    title: qsTr("Hello World")
+    title: qsTr("TexCrafting")
 
     TextureCrafter {
         id: crafter

texturecrafter.cpp

@@ -4,6 +4,18 @@ TextureCrafter::TextureCrafter(QObject *parent)
     : QObject{parent}
 {}
 
+QString TextureCrafter::getOutFilename() {
+    QString outFileName;
+    if (outDir.isValid()) {
+        outFileName = outDir.path();
+        outFileName.append("/out.png");
+    } else {
+        return QString();
+    }
+
+    return outFileName;
+}
+
 QUrl TextureCrafter::packChannels(QVector<QUrl> imagePaths) {
 
     QVector<QImage> sourceImages;
@@ -26,43 +38,83 @@ QUrl TextureCrafter::packChannels(QVector<QUrl> imagePaths) {
         sourceImages.append(newImage);
     }
 
-    QImage outImage(width, height, format);
+    png_structp outPng;
+    png_infop outInfo;
+    FILE *outFile;
+    QString outFilename = getOutFilename();
+    unsigned char *rowBuffer;
+
+    // maybe abstract this?
+    outFile = fopen(outFilename.toLatin1().data(), "wb");
+
+    if (!outFile) {
+        return QUrl();
+    }
+
+    outPng = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+    outInfo = png_create_info_struct(outPng);
+    rowBuffer = (unsigned char*)malloc(sizeof(char) * 3 * width);
+
+    png_init_io(outPng, outFile);
+
+    png_set_IHDR (outPng,
+                outInfo,
+                width,
+                height,
+                8, // TODO: support other bit depths someday
+                PNG_COLOR_TYPE_RGB,
+                PNG_INTERLACE_NONE,
+                PNG_COMPRESSION_TYPE_DEFAULT,
+                PNG_FILTER_TYPE_DEFAULT);
+
+    png_write_info(outPng, outInfo);
 
     // do the channel packing!!
     // theres probably a faster way to do this but eh
-    for (int i = 0; i < width; i++) {
-        for (int j = 0; j < height; j++) {
-            int r, g, b;
+    for (int i = 0; i < height; i++) {
+        memset(rowBuffer, 0, sizeof(char) * 3 * width);
+        for (int j = 0; j < width; j++) {
+            unsigned char r, g, b;
 
             // too eepy for dry
-            r = sourceImages.at(0).pixelColor(i, j).red();
-            g = sourceImages.at(1).pixelColor(i, j).green();
-            b = sourceImages.at(2).pixelColor(i, j).blue();
+            r = sourceImages.at(0).pixelColor(j, i).red();
+            g = sourceImages.at(1).pixelColor(j, i).green();
+            b = sourceImages.at(2).pixelColor(j, i).blue();
 
-            QColor newColor(r, g, b);
-
-            outImage.setPixelColor(i, j, newColor);
+            rowBuffer[j*3+0] = r;
+            rowBuffer[j*3+1] = g;
+            rowBuffer[j*3+2] = b;
         }
+
+        png_write_row(outPng, rowBuffer);
     }
 
-    // write it to a temp file
-    if (outDir.isValid()) {
-        QString outFileName = outDir.path();
-        outFileName.append("/out.png");
+    png_write_end(outPng, NULL);
 
-        printf("wrote to %s\n", outFileName.toLatin1().data());
+    // good soldiers free their memory
+    free(rowBuffer);
+    png_destroy_write_struct(&outPng, &outInfo);
+    fclose(outFile);
+    return QUrl::fromLocalFile(outFilename);
 
-	//TODO: use libpng and do progressive write to update the progress bar
-        if (outImage.save(outFileName)) {
-            printf("cool ^-^\n");
-            return QUrl::fromLocalFile(outFileName);
-        } else {
-            //TODO: return some error value to show the user
-            printf("that dream is fucked it is fucking fucked\n");
-        }
-    } else {
-        printf("chat its so over\n");
-    }
+ //    // write it to a temp file
+ //    if (outDir.isValid()) {
+ //        QString outFileName = outDir.path();
+ //        outFileName.append("/out.png");
+
+ //        printf("wrote to %s\n", outFileName.toLatin1().data());
+
+    // //TODO: use libpng and do progressive write to update the progress bar
+ //        if (outImage.save(outFileName)) {
+ //            printf("cool ^-^\n");
+ //            return QUrl::fromLocalFile(outFileName);
+ //        } else {
+ //            //TODO: return some error value to show the user
+ //            printf("that dream is fucked it is fucking fucked\n");
+ //        }
+ //    } else {
+ //        printf("chat its so over\n");
+ //    }
 
     return QUrl();
     //do we need to close these??? idk lets hope qt handles it

texturecrafter.h

@@ -6,6 +6,8 @@
 #include <QImage>
 #include <QTemporaryDir>
 
+#include <png.h>
+
 class TextureCrafter : public QObject
 {
     Q_OBJECT
@@ -17,6 +19,8 @@ public:
 
 signals:
 private:
+    QString getOutFilename();
+
     QTemporaryDir outDir;
 };