Performance: Use QImage's smoothscaling instead of old private code

For historical reasons, QJpegHandler had its own smoothscaling code.
QImage's scaling has since evolved to become both faster and better, so
avoid code duplication and just use QImage for scaling.

Reviewed-by: Trond

1 files changed, 67 insertions, 507 deletions

diff --git a/src/plugins/imageformats/jpeg/qjpeghandler.cpp b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
index 6cb93ad..4b4712c 100644
--- a/src/plugins/imageformats/jpeg/qjpeghandler.cpp
+++ b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
@@ -52,8 +52,6 @@
 #undef FAR
 #endif
 
-// hw: optimize smoothscaler for returning 24-bit images
-
 // including jpeglib.h seems to be a little messy
 extern "C" {
 // mingw includes rpcndr.h but does not define boolean
@@ -76,433 +74,6 @@ extern "C" {
 
 QT_BEGIN_NAMESPACE
 
-//#define QT_NO_IMAGE_SMOOTHSCALE
-#ifndef QT_NO_IMAGE_SMOOTHSCALE
-class QImageSmoothScalerPrivate;
-class QImageSmoothScaler
-{
-public:
-    QImageSmoothScaler(const int w, const int h, const QImage &src);
-    QImageSmoothScaler(const int srcWidth, const int srcHeight,
-                       const int dstWidth, const int dstHeight);
-
-    virtual ~QImageSmoothScaler(void);
-
-    QImage  scale();
-
-private:
-    QImageSmoothScalerPrivate	*d;
-    virtual QRgb *scanLine(const int line = 0, const QImage *src = 0);
-};
-
-class QImageSmoothScalerPrivate
-{
-public:
-    int	    cols;
-    int	    newcols;
-    int	    rows;
-    int	    newrows;
-    bool    hasAlpha;
-
-    const QImage  *src;
-
-    void setup(const int srcWidth, const int srcHeight, const int dstWidth,
-               const int dstHeight, bool hasAlphaChannel);
-};
-
-QImageSmoothScaler::QImageSmoothScaler(const int w, const int h,
-                                       const QImage &src)
-{
-    d = new QImageSmoothScalerPrivate;
-
-    d->setup(src.width(), src.height(), w, h, src.hasAlphaChannel() );
-    this->d->src = &src;
-}
-
-QImageSmoothScaler::QImageSmoothScaler(const int srcWidth, const int srcHeight,
-                                       const int dstWidth, const int dstHeight)
-{
-    d = new QImageSmoothScalerPrivate;
-    d->setup(srcWidth, srcHeight, dstWidth, dstHeight, 0);
-}
-
-void QImageSmoothScalerPrivate::setup(const int srcWidth, const int srcHeight,
-                                      const int dstWidth, const int dstHeight,
-                                      bool hasAlphaChannel)
-{
-    cols = srcWidth;
-    rows = srcHeight;
-    newcols = dstWidth;
-    newrows = dstHeight;
-    hasAlpha = hasAlphaChannel;
-}
-
-QImageSmoothScaler::~QImageSmoothScaler()
-{
-    delete d;
-}
-
-inline QRgb *QImageSmoothScaler::scanLine(const int line, const QImage *src)
-{
-    return (QRgb*)src->scanLine(line);
-}
-
-/*
-  This function uses code based on pnmscale.c by Jef Poskanzer.
-
-  pnmscale.c - read a portable anymap and scale it
-
-  Copyright (C) 1989, 1991 by Jef Poskanzer.
-
-  Permission to use, copy, modify, and distribute this software and its
-  documentation for any purpose and without fee is hereby granted, provided
-  that the above copyright notice appear in all copies and that both that
-  copyright notice and this permission notice appear in supporting
-  documentation.  This software is provided "as is" without express or
-  implied warranty.
-*/
-
-QImage QImageSmoothScaler::scale()
-{
-    long SCALE;
-    long HALFSCALE;
-    QRgb *xelrow = 0;
-    QRgb *tempxelrow = 0;
-    QRgb *xP;
-    QRgb *nxP;
-    int row, rowsread;
-    int col, needtoreadrow;
-    uchar maxval = 255;
-    qreal xscale, yscale;
-    long sxscale, syscale;
-    long fracrowtofill, fracrowleft;
-    long *as;
-    long *rs;
-    long *gs;
-    long *bs;
-    int rowswritten = 0;
-    QImage dst;
-
-    if (d->cols > 4096) {
-        SCALE = 4096;
-        HALFSCALE = 2048;
-    } else {
-        int fac = 4096;
-        while (d->cols * fac > 4096)
-            fac /= 2;
-
-        SCALE = fac * d->cols;
-        HALFSCALE = fac * d->cols / 2;
-    }
-
-    xscale = (qreal)d->newcols / (qreal)d->cols;
-    yscale = (qreal)d->newrows / (qreal)d->rows;
-    sxscale = (long)(xscale * SCALE);
-    syscale = (long)(yscale * SCALE);
-
-    // shortcut Y scaling if possible
-    if (d->newrows != d->rows)
-        tempxelrow = new QRgb[d->cols];
-
-    if (d->hasAlpha) {
-        as = new long[d->cols];
-        for (col = 0; col < d->cols; ++col)
-            as[col] = HALFSCALE;
-    } else {
-        as = 0;
-    }
-    rs = new long[d->cols];
-    gs = new long[d->cols];
-    bs = new long[d->cols];
-    rowsread = 0;
-    fracrowleft = syscale;
-    needtoreadrow = 1;
-    for (col = 0; col < d->cols; ++col)
-        rs[col] = gs[col] = bs[col] = HALFSCALE;
-    fracrowtofill = SCALE;
-
-    dst = QImage(d->newcols, d->newrows, d->hasAlpha ? QImage::Format_ARGB32 : QImage::Format_RGB32);
-
-    for (row = 0; row < d->newrows; ++row) {
-        // First scale Y from xelrow into tempxelrow.
-        if (d->newrows == d->rows) {
-            // shortcut Y scaling if possible
-            tempxelrow = xelrow = scanLine(rowsread++, d->src);
-        } else {
-            while (fracrowleft < fracrowtofill) {
-                if (needtoreadrow && rowsread < d->rows)
-                    xelrow = scanLine(rowsread++, d->src);
-                for (col = 0, xP = xelrow; col < d->cols; ++col, ++xP) {
-                    if (as) {
-                        as[col] += fracrowleft * qAlpha(*xP);
-                        rs[col] += fracrowleft * qRed(*xP) * qAlpha(*xP) / 255;
-                        gs[col] += fracrowleft * qGreen(*xP) * qAlpha(*xP) / 255;
-                        bs[col] += fracrowleft * qBlue(*xP) * qAlpha(*xP) / 255;
-                    } else {
-                        rs[col] += fracrowleft * qRed(*xP);
-                        gs[col] += fracrowleft * qGreen(*xP);
-                        bs[col] += fracrowleft * qBlue(*xP);
-                    }
-                }
-                fracrowtofill -= fracrowleft;
-                fracrowleft = syscale;
-                needtoreadrow = 1;
-            }
-            // Now fracrowleft is >= fracrowtofill, so we can produce a row.
-            if (needtoreadrow && rowsread < d->rows) {
-                xelrow = scanLine(rowsread++, d->src);
-                needtoreadrow = 0;
-            }
-            for (col = 0, xP = xelrow, nxP = tempxelrow; col < d->cols; ++col, ++xP, ++nxP) {
-                register long a, r, g, b;
-
-                if (as) {
-                    r = rs[col] + fracrowtofill * qRed(*xP) * qAlpha(*xP) / 255;
-                    g = gs[col] + fracrowtofill * qGreen(*xP) * qAlpha(*xP) / 255;
-                    b = bs[col] + fracrowtofill * qBlue(*xP) * qAlpha(*xP) / 255;
-                    a = as[col] + fracrowtofill * qAlpha(*xP);
-                    if (a) {
-                        r = r * 255 / a * SCALE;
-                        g = g * 255 / a * SCALE;
-                        b = b * 255 / a * SCALE;
-                    }
-                } else {
-                    r = rs[col] + fracrowtofill * qRed(*xP);
-                    g = gs[col] + fracrowtofill * qGreen(*xP);
-                    b = bs[col] + fracrowtofill * qBlue(*xP);
-                    a = 0; // unwarn
-                }
-                r /= SCALE;
-                if (r > maxval)
-                    r = maxval;
-                g /= SCALE;
-                if (g > maxval)
-                    g = maxval;
-                b /= SCALE;
-                if (b > maxval)
-                    b = maxval;
-                if (as) {
-                    a /= SCALE;
-                    if (a > maxval)
-                        a = maxval;
-                    *nxP = qRgba((int)r, (int)g, (int)b, (int)a);
-                    as[col] = HALFSCALE;
-                } else {
-                    *nxP = qRgb((int)r, (int)g, (int)b);
-                }
-                rs[col] = gs[col] = bs[col] = HALFSCALE;
-            }
-            fracrowleft -= fracrowtofill;
-            if (fracrowleft == 0) {
-                fracrowleft = syscale;
-                needtoreadrow = 1;
-            }
-            fracrowtofill = SCALE;
-        }
-
-        // Now scale X from tempxelrow into dst and write it out.
-        if (d->newcols == d->cols) {
-            // shortcut X scaling if possible
-            memcpy(dst.scanLine(rowswritten++), tempxelrow, d->newcols * 4);
-        } else {
-            register long a, r, g, b;
-            register long fraccoltofill, fraccolleft = 0;
-            register int needcol;
-
-            nxP = (QRgb *)dst.scanLine(rowswritten++);
-            QRgb *nxPEnd = nxP + d->newcols;
-            fraccoltofill = SCALE;
-            a = r = g = b = HALFSCALE;
-            needcol = 0;
-            for (col = 0, xP = tempxelrow; col < d->cols; ++col, ++xP) {
-                fraccolleft = sxscale;
-                while (fraccolleft >= fraccoltofill) {
-                    if (needcol) {
-                        ++nxP;
-                        a = r = g = b = HALFSCALE;
-                    }
-                    if (as) {
-                        r += fraccoltofill * qRed(*xP) * qAlpha(*xP) / 255;
-                        g += fraccoltofill * qGreen(*xP) * qAlpha(*xP) / 255;
-                        b += fraccoltofill * qBlue(*xP) * qAlpha(*xP) / 255;
-                        a += fraccoltofill * qAlpha(*xP);
-                        if (a) {
-                            r = r * 255 / a * SCALE;
-                            g = g * 255 / a * SCALE;
-                            b = b * 255 / a * SCALE;
-                        }
-                    } else {
-                        r += fraccoltofill * qRed(*xP);
-                        g += fraccoltofill * qGreen(*xP);
-                        b += fraccoltofill * qBlue(*xP);
-                    }
-                    r /= SCALE;
-                    if (r > maxval)
-                        r = maxval;
-                    g /= SCALE;
-                    if (g > maxval)
-                        g = maxval;
-                    b /= SCALE;
-                    if (b > maxval)
-                        b = maxval;
-                    if (as) {
-                        a /= SCALE;
-                        if (a > maxval)
-                            a = maxval;
-                        *nxP = qRgba((int)r, (int)g, (int)b, (int)a);
-                    } else {
-                        *nxP = qRgb((int)r, (int)g, (int)b);
-                    }
-                    fraccolleft -= fraccoltofill;
-                    fraccoltofill = SCALE;
-                    needcol = 1;
-                }
-                if (fraccolleft > 0) {
-                    if (needcol) {
-                        ++nxP;
-                        a = r = g = b = HALFSCALE;
-                        needcol = 0;
-                    }
-                    if (as) {
-                        a += fraccolleft * qAlpha(*xP);
-                        r += fraccolleft * qRed(*xP) * qAlpha(*xP) / 255;
-                        g += fraccolleft * qGreen(*xP) * qAlpha(*xP) / 255;
-                        b += fraccolleft * qBlue(*xP) * qAlpha(*xP) / 255;
-                    } else {
-                        r += fraccolleft * qRed(*xP);
-                        g += fraccolleft * qGreen(*xP);
-                        b += fraccolleft * qBlue(*xP);
-                    }
-                    fraccoltofill -= fraccolleft;
-                }
-            }
-            if (fraccoltofill > 0) {
-                --xP;
-                if (as) {
-                    a += fraccolleft * qAlpha(*xP);
-                    r += fraccoltofill * qRed(*xP) * qAlpha(*xP) / 255;
-                    g += fraccoltofill * qGreen(*xP) * qAlpha(*xP) / 255;
-                    b += fraccoltofill * qBlue(*xP) * qAlpha(*xP) / 255;
-                    if (a) {
-                        r = r * 255 / a * SCALE;
-                        g = g * 255 / a * SCALE;
-                        b = b * 255 / a * SCALE;
-                    }
-                } else {
-                    r += fraccoltofill * qRed(*xP);
-                    g += fraccoltofill * qGreen(*xP);
-                    b += fraccoltofill * qBlue(*xP);
-                }
-            }
-            if (nxP < nxPEnd) {
-                r /= SCALE;
-                if (r > maxval)
-                    r = maxval;
-                g /= SCALE;
-                if (g > maxval)
-                    g = maxval;
-                b /= SCALE;
-                if (b > maxval)
-                    b = maxval;
-                if (as) {
-                    a /= SCALE;
-                    if (a > maxval)
-                        a = maxval;
-                    *nxP = qRgba((int)r, (int)g, (int)b, (int)a);
-                } else {
-                    *nxP = qRgb((int)r, (int)g, (int)b);
-                }
-                while (++nxP != nxPEnd)
-                    nxP[0] = nxP[-1];
-            }
-        }
-    }
-
-    if (d->newrows != d->rows && tempxelrow)// Robust, tempxelrow might be 0 1 day
-        delete [] tempxelrow;
-    if (as)				// Avoid purify complaint
-        delete [] as;
-    if (rs)				// Robust, rs might be 0 one day
-        delete [] rs;
-    if (gs)				// Robust, gs might be 0 one day
-        delete [] gs;
-    if (bs)				// Robust, bs might be 0 one day
-        delete [] bs;
-
-    return dst;
-}
-
-class jpegSmoothScaler : public QImageSmoothScaler
-{
-public:
-    jpegSmoothScaler(struct jpeg_decompress_struct *info, const QSize& dstSize, const QRect& clipRect)
-        : QImageSmoothScaler(clipRect.width(), clipRect.height(),
-                             dstSize.width(), dstSize.height())
-    {
-        cinfo = info;
-        clip = clipRect;
-        imageCache = QImage(info->output_width, 1, QImage::Format_RGB32);
-    }
-
-private:
-    QRect   clip;
-    QImage  imageCache;
-    struct jpeg_decompress_struct *cinfo;
-
-    QRgb *scanLine(const int line = 0, const QImage *src = 0)
-    {
-	QRgb    *out;
-	uchar	*in;
-
-	Q_UNUSED(line);
-	Q_UNUSED(src);
-
-        uchar* data = imageCache.bits();
-
-        // Read ahead if we haven't reached the first clipped scanline yet.
-        while (int(cinfo->output_scanline) < clip.y() &&
-               cinfo->output_scanline < cinfo->output_height)
-	    jpeg_read_scanlines(cinfo, &data, 1);
-
-        // Read the next scanline.  We assume that "line"
-        // will never be >= clip.height().
-	jpeg_read_scanlines(cinfo, &data, 1);
-        if (cinfo->output_scanline == cinfo->output_height)
-            jpeg_finish_decompress(cinfo);
-
-	out = ((QRgb*)data) + clip.x();
-
-	//
-	// The smooth scale algorithm only works on 32-bit images;
-	// convert from (8|24) bits to 32.
-	//
-	if (cinfo->output_components == 1) {
-	    in = data + clip.right();
-	    for (int i = clip.width(); i--; ) {
-		out[i] = qRgb(*in, *in, *in);
-		in--;
-	    }
-        } else if (cinfo->out_color_space == JCS_CMYK) {
-            in = data + clip.right() * 4;
-            for (int i = clip.width(); i--; ) {
-                int k = in[3];
-                out[i] = qRgb(k * in[0] / 255, k * in[1] / 255, k * in[2] / 255);
-                in -= 4;
-            }
-        } else {
-	    in = data + clip.right() * 3;
-	    for (int i = clip.width(); i--; ) {
-		out[i] = qRgb(in[0], in[1], in[2]);
-		in -= 3;
-	    }
-	}
-
-	return out;
-    }
-
-};
-#endif
-
 struct my_error_mgr : public jpeg_error_mgr {
     jmp_buf setjmp_buffer;
 };
@@ -844,93 +415,82 @@ static bool read_jpeg_image(QIODevice *device, QImage *outImage,
             clip = clip.intersected(imageRect);
         }
 
-#ifndef QT_NO_IMAGE_SMOOTHSCALE
-        if (scaledSize.isValid() && scaledSize != clip.size()
-            && quality >= HIGH_QUALITY_THRESHOLD) {
+        // Allocate memory for the clipped QImage.
+        if (!ensureValidImage(outImage, &cinfo, clip.size()))
+            longjmp(jerr.setjmp_buffer, 1);
+
+        // Avoid memcpy() overhead if grayscale with no clipping.
+        bool quickGray = (cinfo.output_components == 1 &&
+                          clip == imageRect);
+        if (!quickGray) {
+            // Ask the jpeg library to allocate a temporary row.
+            // The library will automatically delete it for us later.
+            // The libjpeg docs say we should do this before calling
+            // jpeg_start_decompress().  We can't use "new" here
+            // because we are inside the setjmp() block and an error
+            // in the jpeg input stream would cause a memory leak.
+            JSAMPARRAY rows = (cinfo.mem->alloc_sarray)
+                              ((j_common_ptr)&cinfo, JPOOL_IMAGE,
+                               cinfo.output_width * cinfo.output_components, 1);
 
             (void) jpeg_start_decompress(&cinfo);
 
-            jpegSmoothScaler scaler(&cinfo, scaledSize, clip);
-            *outImage = scaler.scale();
-        } else
-#endif
-        {
-            // Allocate memory for the clipped QImage.
-            if (!ensureValidImage(outImage, &cinfo, clip.size()))
-                longjmp(jerr.setjmp_buffer, 1);
-
-            // Avoid memcpy() overhead if grayscale with no clipping.
-            bool quickGray = (cinfo.output_components == 1 &&
-                              clip == imageRect);
-            if (!quickGray) {
-                // Ask the jpeg library to allocate a temporary row.
-                // The library will automatically delete it for us later.
-                // The libjpeg docs say we should do this before calling
-                // jpeg_start_decompress().  We can't use "new" here
-                // because we are inside the setjmp() block and an error
-                // in the jpeg input stream would cause a memory leak.
-                JSAMPARRAY rows = (cinfo.mem->alloc_sarray)
-                    ((j_common_ptr)&cinfo, JPOOL_IMAGE,
-                     cinfo.output_width * cinfo.output_components, 1);
-
-                (void) jpeg_start_decompress(&cinfo);
-
-                while (cinfo.output_scanline < cinfo.output_height) {
-                    int y = int(cinfo.output_scanline) - clip.y();
-                    if (y >= clip.height())
-                        break;      // We've read the entire clip region, so abort.
-
-                    (void) jpeg_read_scanlines(&cinfo, rows, 1);
-
-                    if (y < 0)
-                        continue;   // Haven't reached the starting line yet.
-
-                    if (cinfo.output_components == 3) {
-                        // Expand 24->32 bpp.
-                        uchar *in = rows[0] + clip.x() * 3;
-                        QRgb *out = (QRgb*)outImage->scanLine(y);
-                        for (int i = 0; i < clip.width(); ++i) {
-                            *out++ = qRgb(in[0], in[1], in[2]);
-                            in += 3;
-                        }
-                    } else if (cinfo.out_color_space == JCS_CMYK) {
-                        // Convert CMYK->RGB.
-                        uchar *in = rows[0] + clip.x() * 4;
-                        QRgb *out = (QRgb*)outImage->scanLine(y);
-                        for (int i = 0; i < clip.width(); ++i) {
-                            int k = in[3];
-                            *out++ = qRgb(k * in[0] / 255, k * in[1] / 255,
-                                          k * in[2] / 255);
-                            in += 4;
-                        }
-                    } else if (cinfo.output_components == 1) {
-                        // Grayscale.
-                        memcpy(outImage->scanLine(y),
-                               rows[0] + clip.x(), clip.width());
+            while (cinfo.output_scanline < cinfo.output_height) {
+                int y = int(cinfo.output_scanline) - clip.y();
+                if (y >= clip.height())
+                    break;      // We've read the entire clip region, so abort.
+
+                (void) jpeg_read_scanlines(&cinfo, rows, 1);
+
+                if (y < 0)
+                    continue;   // Haven't reached the starting line yet.
+
+                if (cinfo.output_components == 3) {
+                    // Expand 24->32 bpp.
+                    uchar *in = rows[0] + clip.x() * 3;
+                    QRgb *out = (QRgb*)outImage->scanLine(y);
+                    for (int i = 0; i < clip.width(); ++i) {
+                        *out++ = qRgb(in[0], in[1], in[2]);
+                        in += 3;
                     }
-                }
-            } else {
-                // Load unclipped grayscale data directly into the QImage.
-                (void) jpeg_start_decompress(&cinfo);
-                while (cinfo.output_scanline < cinfo.output_height) {
-                    uchar *row = outImage->scanLine(cinfo.output_scanline);
-                    (void) jpeg_read_scanlines(&cinfo, &row, 1);
+                } else if (cinfo.out_color_space == JCS_CMYK) {
+                    // Convert CMYK->RGB.
+                    uchar *in = rows[0] + clip.x() * 4;
+                    QRgb *out = (QRgb*)outImage->scanLine(y);
+                    for (int i = 0; i < clip.width(); ++i) {
+                        int k = in[3];
+                        *out++ = qRgb(k * in[0] / 255, k * in[1] / 255,
+                                      k * in[2] / 255);
+                        in += 4;
+                    }
+                } else if (cinfo.output_components == 1) {
+                    // Grayscale.
+                    memcpy(outImage->scanLine(y),
+                           rows[0] + clip.x(), clip.width());
                 }
             }
+        } else {
+            // Load unclipped grayscale data directly into the QImage.
+            (void) jpeg_start_decompress(&cinfo);
+            while (cinfo.output_scanline < cinfo.output_height) {
+                uchar *row = outImage->scanLine(cinfo.output_scanline);
+                (void) jpeg_read_scanlines(&cinfo, &row, 1);
+            }
+        }
 
-            if (cinfo.output_scanline == cinfo.output_height)
-                (void) jpeg_finish_decompress(&cinfo);
+        if (cinfo.output_scanline == cinfo.output_height)
+            (void) jpeg_finish_decompress(&cinfo);
 
-            if (cinfo.density_unit == 1) {
-                outImage->setDotsPerMeterX(int(100. * cinfo.X_density / 2.54));
-                outImage->setDotsPerMeterY(int(100. * cinfo.Y_density / 2.54));
-            } else if (cinfo.density_unit == 2) {
-                outImage->setDotsPerMeterX(int(100. * cinfo.X_density));
-                outImage->setDotsPerMeterY(int(100. * cinfo.Y_density));
-            }
+        if (cinfo.density_unit == 1) {
+            outImage->setDotsPerMeterX(int(100. * cinfo.X_density / 2.54));
+            outImage->setDotsPerMeterY(int(100. * cinfo.Y_density / 2.54));
+        } else if (cinfo.density_unit == 2) {
+            outImage->setDotsPerMeterX(int(100. * cinfo.X_density));
+            outImage->setDotsPerMeterY(int(100. * cinfo.Y_density));
+        }
 
-            if (scaledSize.isValid() && scaledSize != clip.size())
-                *outImage = outImage->scaled(scaledSize, Qt::IgnoreAspectRatio, Qt::FastTransformation);
+        if (scaledSize.isValid() && scaledSize != clip.size()) {
+            *outImage = outImage->scaled(scaledSize, Qt::IgnoreAspectRatio, quality >= HIGH_QUALITY_THRESHOLD ? Qt::SmoothTransformation : Qt::FastTransformation);
         }
     }