reimplemnt png handler

based on code I wrote some time ago

Signed-off-by: Ivailo Monev <xakepa10@gmail.com>

CMakeLists.txt

@@ -188,11 +188,11 @@ set_package_properties(Threads PROPERTIES
     TYPE REQUIRED
 )
 
-find_package(PNG)
-set_package_properties(PNG PROPERTIES
+find_package(SPNG)
+set_package_properties(SPNG PROPERTIES
     PURPOSE "PNG format handler"
-    DESCRIPTION "A collection of routines used to create PNG format graphics files"
-    URL "http://www.libpng.org/pub/png/libpng.html"
+    DESCRIPTION "Simple, modern libpng alternative"
+    URL "https://libspng.org/"
     TYPE REQUIRED
 )
 

cmake/modules/FindSPNG.cmake

@@ -0,0 +1,31 @@
+# Try to find SPNG, once done this will define:
+#
+#  SPNG_FOUND - system has SPNG
+#  SPNG_INCLUDES - the SPNG include directory
+#  SPNG_LIBRARIES - the libraries needed to use SPNG
+#
+# Copyright (C) 2023 Ivailo Monev <xakepa10@gmail.com>
+#
+# Redistribution and use is allowed according to the terms of the BSD license.
+
+find_package(PkgConfig REQUIRED)
+include(FindPackageHandleStandardArgs)
+
+pkg_check_modules(PC_SPNG QUIET spng)
+
+find_path(SPNG_INCLUDES
+    NAMES spng.h
+    HINTS $ENV{SPNGDIR}/include ${PC_SPNG_INCLUDEDIR}
+)
+
+find_library(SPNG_LIBRARIES
+    NAMES spng
+    HINTS $ENV{SPNGDIR}/lib ${PC_SPNG_LIBDIR}
+)
+
+find_package_handle_standard_args(SPNG
+    VERSION_VAR PC_SPNG_VERSION
+    REQUIRED_VARS SPNG_LIBRARIES SPNG_INCLUDES
+)
+
+mark_as_advanced(SPNG_INCLUDES SPNG_LIBRARIES)

src/gui/CMakeLists.txt

@@ -1,9 +1,9 @@
-add_definitions(${PNG_DEFINITIONS})
+# add_definitions()
 set(EXTRA_GUI_LIBS
     KtCore
     ${FREETYPE_LIBRARIES}
     ${X11_X11_LIB}
-    ${PNG_LIBRARIES}
+    ${SPNG_LIBRARIES}
     ${DEFLATE_LIBRARIES}
 )
 
@@ -200,7 +200,7 @@ include_directories(
     ${CMAKE_BINARY_DIR}/include/QtGui
     ${FREETYPE_INCLUDE_DIRS}
     ${X11_INCLUDE_DIR}
-    ${PNG_INCLUDE_DIRS}
+    ${SPNG_INCLUDES}
     ${DEFLATE_INCLUDES}
 )
 

src/gui/image/qpnghandler.cpp

@@ -1,7 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2015 The Qt Company Ltd.
-** Copyright (C) 2016 Ivailo Monev
+** Copyright (C) 2023 Ivailo Monev
 **
 ** This file is part of the QtGui module of the Katie Toolkit.
 **
@@ -23,64 +22,45 @@
 #include "qiodevice.h"
 #include "qvariant.h"
 #include "qimage.h"
-#include "qimage_p.h"
-#include "qdrawhelper_p.h"
 #include "qcorecommon_p.h"
-#include "qguicommon_p.h"
+#include "qdebug.h"
 
-#include <png.h>
-#include <pngconf.h>
+#include <spng.h>
+
+// for reference:
+// https://www.w3.org/TR/PNG-Chunks.html
 
 QT_BEGIN_NAMESPACE
 
-#if Q_BYTE_ORDER == Q_BIG_ENDIAN
-#  define QFILLER_ORDER PNG_FILLER_BEFORE
-#else
-#  define QFILLER_ORDER PNG_FILLER_AFTER
-#endif
-
-/*
-  All PNG files load to the minimal QImage equivalent.
-
-  All QImage formats output to reasonably efficient PNG equivalents.
-  Never to grayscale.
-*/
-
-extern "C" {
-
-static void qt_png_warning(png_structp /*png_ptr*/, png_const_charp message)
+int spng_read_proc(spng_ctx *ctx, void *user, void *dst_src, size_t length)
 {
-    qWarning("libpng warning: %s", message);
-}
-
-static void qt_png_read(png_structp png_ptr, png_bytep data, png_size_t length)
-{
-    QPngHandler *handler = (QPngHandler *)png_get_io_ptr(png_ptr);
-
-    png_size_t nr = handler->device()->read((char*)data, length);
-    if (nr != length) {
-        png_error(png_ptr, "Read error");
+    // qDebug() << Q_FUNC_INFO << length;
+    Q_UNUSED(ctx);
+    QIODevice* iodevice = static_cast<QIODevice*>(user);
+    char* dst = static_cast<char*>(dst_src);
+    const qint64 result = iodevice->read(dst, length);
+    if (result <= 0) {
+        return SPNG_IO_ERROR;
     }
+    return SPNG_OK;
 }
 
-static void qt_png_write(png_structp png_ptr, png_bytep data, png_size_t length)
+int spng_write_proc(spng_ctx *ctx, void *user, void *dst_src, size_t length)
 {
-    QPngHandler *handler = (QPngHandler *)png_get_io_ptr(png_ptr);
-
-    png_size_t nr = handler->device()->write((char*)data, length);
-    if (nr != length) {
-        png_error(png_ptr, "Write error");
+    // qDebug() << Q_FUNC_INFO << length;
+    Q_UNUSED(ctx);
+    QIODevice* iodevice = static_cast<QIODevice*>(user);
+    const char* src = static_cast<char*>(dst_src);
+    const qint64 result = iodevice->write(src, length);
+    if (result <= 0) {
+        return SPNG_IO_ERROR;
     }
+    return SPNG_OK;
 }
 
-static void qt_png_flush(png_structp /* png_ptr */)
-{
-}
-
-}
 
 QPngHandler::QPngHandler()
-    : m_compression(1)
+    : m_complevel(1)
 {
 }
 
@@ -100,185 +80,174 @@ bool QPngHandler::canRead() const
 
 bool QPngHandler::read(QImage *image)
 {
-    if (!canRead()) {
+    spng_ctx *spngctx = spng_ctx_new(static_cast<spng_ctx_flags>(0));
+    if (Q_UNLIKELY(!spngctx)) {
+        qWarning("QPngHandler::read() Could not create context");
         return false;
     }
 
-    png_struct *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
-    if (!png_ptr) {
+    int spngresult = spng_set_png_stream(spngctx, spng_read_proc, device());
+    if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+        qWarning("QPngHandler::read() Could not set stream: %s", spng_strerror(spngresult));
+        spng_ctx_free(spngctx);
         return false;
     }
 
-    png_set_error_fn(png_ptr, 0, 0, qt_png_warning);
-
-    png_info *info_ptr = png_create_info_struct(png_ptr);
-    if (!info_ptr) {
-        png_destroy_read_struct(&png_ptr, 0, 0);
+    struct spng_ihdr spngihdr;
+    ::memset(&spngihdr, 0, sizeof(struct spng_ihdr));
+    spngresult = spng_get_ihdr(spngctx, &spngihdr);
+    if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+        qWarning("QPngHandler::read() Could not get IHDR: %s", spng_strerror(spngresult));
+        spng_ctx_free(spngctx);
         return false;
     }
 
-    png_info *end_info = png_create_info_struct(png_ptr);
-    if (!end_info) {
-        png_destroy_read_struct(&png_ptr, &info_ptr, 0);
+    *image = QImage(spngihdr.width, spngihdr.height, QImage::Format_ARGB32);
+    if (Q_UNLIKELY(image->isNull())) {
+        qWarning("QPngHandler::read() Could not create image");
+        spng_ctx_free(spngctx);
         return false;
     }
 
-    if (setjmp(png_jmpbuf(png_ptr))) {
-        png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+    spngresult = spng_decode_image(
+        spngctx,
+        image->bits(), image->byteCount(),
+        SPNG_FMT_RGBA8,
+        SPNG_DECODE_TRNS
+    );
+    if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+        qWarning("QPngHandler::read() Could not decode image: %s", spng_strerror(spngresult));
+        *image = QImage();
+        spng_ctx_free(spngctx);
         return false;
     }
 
-    png_set_read_fn(png_ptr, this, qt_png_read);
-    png_read_info(png_ptr, info_ptr);
-
-    png_uint_32 width = 0;
-    png_uint_32 height = 0;
-    int bit_depth;
-    int color_type;
-    png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, 0, 0, 0);
-    const int passes = png_set_interlace_handling(png_ptr);
-
-    if (bit_depth == 16) {
-        png_set_strip_16(png_ptr);
-    }
-
-    png_set_expand(png_ptr);
-
-    if (color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
-        png_set_gray_to_rgb(png_ptr);
-    } else if (color_type == PNG_COLOR_TYPE_PALETTE) {
-        png_set_palette_to_rgb(png_ptr);
-    }
-
-    QImage::Format format = QImage::Format_ARGB32;
-    // Only add filler if no alpha, or we can get 5 channel data.
-    if (!(color_type & PNG_COLOR_MASK_ALPHA)
-        && !png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
-        png_set_filler(png_ptr, 0xff, QFILLER_ORDER);
-        // We want 4 bytes, but it isn't an alpha channel
-        format = QImage::Format_RGB32;
-    }
-    *image = QImage(width, height, format);
-    if (image->isNull()) {
-        png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
-        return false;
-    }
-
-#if Q_BYTE_ORDER == Q_BIG_ENDIAN
-    png_set_swap_alpha(png_ptr);
-#endif
-
-    png_read_update_info(png_ptr, info_ptr);
-
-    // Qt==ARGB==Big(ARGB)==Little(BGRA)
-#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
-    png_set_bgr(png_ptr);
-#endif
-
-    uchar *data = image->d->data;
-    const int bpl = image->bytesPerLine();
-    for (int p = 0; p < passes; p++) {
-        for (uint y = 0; y < height; y++) {
-            png_read_row(png_ptr, QFAST_SCAN_LINE(data, bpl, y), NULL);
-        }
-    }
-
-    png_read_end(png_ptr, end_info);
-
-    png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
-
+    *image = image->rgbSwapped();
+    spng_ctx_free(spngctx);
     return true;
 }
 
 bool QPngHandler::write(const QImage &image)
 {
-    QImage copy = image.convertToFormat(image.hasAlphaChannel() ? QImage::Format_ARGB32 : QImage::Format_RGB32);
-    const int height = copy.height();
+    const QImage copy = image.convertToFormat(QImage::Format_ARGB32).rgbSwapped();
 
-    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
-    if (!png_ptr) {
+    spng_ctx *spngctx = spng_ctx_new(SPNG_CTX_ENCODER);
+    if (Q_UNLIKELY(!spngctx)) {
+        qWarning("QPngHandler::write() Could not create context");
         return false;
     }
 
-    png_set_error_fn(png_ptr, 0, 0, qt_png_warning);
-
-    png_infop info_ptr = png_create_info_struct(png_ptr);
-    if (!info_ptr) {
-        png_destroy_write_struct(&png_ptr, 0);
+    int spngresult = spng_set_png_stream(spngctx, spng_write_proc, device());
+    if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+        qWarning("QPngHandler::write() Could not set stream: %s", spng_strerror(spngresult));
+        spng_ctx_free(spngctx);
         return false;
     }
 
-    if (setjmp(png_jmpbuf(png_ptr))) {
-        png_destroy_write_struct(&png_ptr, &info_ptr);
+    struct spng_ihdr spngihdr;
+    ::memset(&spngihdr, 0, sizeof(struct spng_ihdr));
+    spngihdr.width = copy.width();
+    spngihdr.height = copy.height();
+    spngihdr.bit_depth = 8;
+    spngihdr.color_type = SPNG_COLOR_TYPE_TRUECOLOR_ALPHA;
+    spngihdr.compression_method = 0; // no enum for it
+    spngihdr.filter_method = SPNG_FILTER_NONE;
+    spngihdr.interlace_method = SPNG_INTERLACE_NONE;
+    spngresult = spng_set_ihdr(spngctx, &spngihdr);
+    if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+        qWarning("QPngHandler::write() Could not set IHDR: %s", spng_strerror(spngresult));
+        spng_ctx_free(spngctx);
         return false;
     }
 
-    png_set_write_fn(png_ptr, (void*)this, qt_png_write, qt_png_flush);
-
-    int color_type = 0;
-    if (copy.hasAlphaChannel()) {
-        color_type = PNG_COLOR_TYPE_RGB_ALPHA;
-    } else {
-        color_type = PNG_COLOR_TYPE_RGB;
+    spngresult = spng_set_option(spngctx, SPNG_IMG_COMPRESSION_LEVEL, m_complevel);
+    if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+        qWarning("QPngHandler::write() Could not set image compression level: %s", spng_strerror(spngresult));
+        spng_ctx_free(spngctx);
+        return false;
     }
 
-    png_set_IHDR(png_ptr, info_ptr, copy.width(), height,
-                 8, // per channel
-                 color_type, 0, 0, 0);       // sets #channels
-
-    png_color_8 sig_bit;
-    sig_bit.red = 8;
-    sig_bit.green = 8;
-    sig_bit.blue = 8;
-    sig_bit.alpha = copy.hasAlphaChannel() ? 8 : 0;
-    png_set_sBIT(png_ptr, info_ptr, &sig_bit);
-    png_set_compression_level(png_ptr, m_compression);
-
-#if Q_BYTE_ORDER == Q_BIG_ENDIAN
-    // Swap ARGB to RGBA (normal PNG format) before saving on
-    // BigEndian machines
-    png_set_swap_alpha(png_ptr);
-#elif Q_BYTE_ORDER == Q_LITTLE_ENDIAN
-    // Qt==ARGB==Big(ARGB)==Little(BGRA). But RGB888 is RGB regardless
-    png_set_bgr(png_ptr);
-#endif
-
-    png_write_info(png_ptr, info_ptr);
-
-    png_set_packing(png_ptr);
-
-    if (color_type == PNG_COLOR_TYPE_RGB) {
-        png_set_filler(png_ptr, 0, QFILLER_ORDER);
+    spngresult = spng_encode_image(
+        spngctx,
+        copy.constBits(), copy.byteCount(),
+        SPNG_FMT_PNG,
+        SPNG_ENCODE_FINALIZE
+    );
+    if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+        qWarning("QPngHandler::write() Could not encode image: %s", spng_strerror(spngresult));
+        spng_ctx_free(spngctx);
+        return false;
     }
 
-    for (int y = 0; y < height; y++) {
-        png_write_row(png_ptr, (png_const_bytep)copy.constScanLine(y));
-    }
-    png_write_end(png_ptr, info_ptr);
-
-    png_destroy_write_struct(&png_ptr, &info_ptr);
-
+    spng_ctx_free(spngctx);
     return true;
 }
 
-bool QPngHandler::supportsOption(QImageIOHandler::ImageOption option) const
+QVariant QPngHandler::option(QImageIOHandler::ImageOption option) const
 {
-    return (option == QImageIOHandler::CompressionLevel);
+    if (option == QImageIOHandler::Size) {
+        const qint64 devicepos = device()->pos();
+
+        spng_ctx *spngctx = spng_ctx_new(static_cast<spng_ctx_flags>(0));
+        if (Q_UNLIKELY(!spngctx)) {
+            qWarning("QPngHandler::option() Could not create context");
+            return false;
+        }
+
+        int spngresult = spng_set_png_stream(spngctx, spng_read_proc, device());
+        if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+            qWarning("QPngHandler::option() Could not set stream: %s", spng_strerror(spngresult));
+            spng_ctx_free(spngctx);
+            return false;
+        }
+
+        struct spng_ihdr spngihdr;
+        ::memset(&spngihdr, 0, sizeof(struct spng_ihdr));
+        spngresult = spng_get_ihdr(spngctx, &spngihdr);
+        if (Q_UNLIKELY(spngresult != SPNG_OK)) {
+            qWarning("QPngHandler::option() Could not get IHDR: %s", spng_strerror(spngresult));
+            spng_ctx_free(spngctx);
+            device()->seek(devicepos);
+            return false;
+        }
+
+        spng_ctx_free(spngctx);
+        device()->seek(devicepos);
+        return QSize(spngihdr.width, spngihdr.height);
+    } else if (option == QImageIOHandler::CompressionLevel) {
+        return QVariant(m_complevel);
+    }
+    return QVariant();
 }
 
 void QPngHandler::setOption(QImageIOHandler::ImageOption option, const QVariant &value)
 {
     if (option == QImageIOHandler::CompressionLevel) {
-        const int newlevel = value.toInt();
-        if (Q_UNLIKELY(newlevel < 0 || newlevel > 9)) {
-            qWarning("QPngHandler::setOption() invalid compression level value");
-            m_compression = 1;
+        const int newcomplevel = value.toInt();
+        if (Q_UNLIKELY(newcomplevel < 0 || newcomplevel > 9)) {
+            qWarning("QPngHandler::setOption() Invalid compression level (%d)", newcomplevel);
+            m_complevel = 1;
         } else {
-            m_compression = newlevel;
+            m_complevel = newcomplevel;
         }
     }
 }
 
+bool QPngHandler::supportsOption(QImageIOHandler::ImageOption option) const
+{
+    switch (option) {
+        case QImageIOHandler::Size:
+        case QImageIOHandler::CompressionLevel: {
+            return true;
+        }
+        default: {
+            return false;
+        }
+    }
+    Q_UNREACHABLE();
+    return false;
+}
+
 QByteArray QPngHandler::name() const
 {
     return "png";
@@ -287,16 +256,16 @@ QByteArray QPngHandler::name() const
 bool QPngHandler::canRead(QIODevice *device)
 {
     if (Q_UNLIKELY(!device)) {
-        qWarning("QPngHandler::canRead() called with no device");
+        qWarning("QPngHandler::canRead() Called with no device");
         return false;
     }
 
     QSTACKARRAY(char, head, 8);
-    if (device->peek(head, sizeof(head)) != sizeof(head))
+    if (device->peek(head, sizeof(head)) != sizeof(head)) {
         return false;
+    }
 
-    static const uchar pngheader[]
-        = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
+    static const uchar pngheader[] = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
     return (::memcmp(head, pngheader, 8) == 0);
 }
 

src/gui/image/qpnghandler_p.h

@@ -1,7 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2015 The Qt Company Ltd.
-** Copyright (C) 2016 Ivailo Monev
+** Copyright (C) 2023 Ivailo Monev
 **
 ** This file is part of the QtGui module of the Katie Toolkit.
 **
@@ -47,15 +46,16 @@ public:
     bool read(QImage *image) final;
     bool write(const QImage &image) final;
 
-    bool supportsOption(QImageIOHandler::ImageOption option) const final;
+    QVariant option(QImageIOHandler::ImageOption option) const final;
     void setOption(QImageIOHandler::ImageOption option, const QVariant &value) final;
+    bool supportsOption(QImageIOHandler::ImageOption option) const final;
 
     QByteArray name() const final;
 
     static bool canRead(QIODevice *device);
 
 private:
-    int m_compression;
+    int m_complevel;
 };
 
 QT_END_NAMESPACE