Compressed texture binding for QtOpenGL: ETC1 and PVRTC

The QGLContext::bindTexture(QString) function has been augmented
with support for ETC1, PVRTC2, and PVRTC4 compressed textures,
in addition to the existing DDS support.

The QGLPixmapData class has also been modified to recognize
compressed texture formats in fromFile() and fromData().

This change also fixes a bug in bindTexture() that prevented
the same compressed texture file from being bound in multiple
contexts.  There is now a separate file cache for each context group.

Task-number: QT-2547
Reviewed-by: Trond

5 files changed, 461 insertions, 118 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 94b8aa5..b376901 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -127,18 +127,6 @@ Q_GLOBAL_STATIC(QGLDefaultOverlayFormat, defaultOverlayFormatInstance)
 QGLExtensions::Extensions QGLExtensions::glExtensions = 0;
 bool QGLExtensions::nvidiaFboNeedsFinish = false;
 
-#ifndef APIENTRY
-# define APIENTRY
-#endif
-typedef void (APIENTRY *pfn_glCompressedTexImage2DARB) (GLenum, GLint, GLenum, GLsizei,
-                                                        GLsizei, GLint, GLsizei, const GLvoid *);
-static pfn_glCompressedTexImage2DARB qt_glCompressedTexImage2DARB = 0;
-
-
-#ifndef APIENTRY
-#define APIENTRY
-#endif
-
 Q_GLOBAL_STATIC(QGLSignalProxy, theSignalProxy)
 QGLSignalProxy *QGLSignalProxy::instance()
 {
@@ -1887,118 +1875,42 @@ void QGLContextPrivate::cleanup()
 {
 }
 
-typedef QHash<QString, GLuint> QGLDDSCache;
-Q_GLOBAL_STATIC(QGLDDSCache, qgl_dds_cache)
-
 /*!
     \overload
 
-    Reads the DirectDrawSurface (DDS) compressed file \a fileName and
-    generates a 2D GL texture from it.
+    Reads the compressed texture file \a fileName and generates a 2D GL
+    texture from it.
 
-    Only the DXT1, DXT3 and DXT5 DDS formats are supported.
+    This function can load DirectDrawSurface (DDS) textures in the
+    DXT1, DXT3 and DXT5 DDS formats if the \c GL_ARB_texture_compression
+    and \c GL_EXT_texture_compression_s3tc extensions are supported.
 
-    Note that this will only work if the implementation supports the
-    \c GL_ARB_texture_compression and \c GL_EXT_texture_compression_s3tc
-    extensions.
+    Since 4.6.1, textures in the ETC1 format can be loaded if the
+    \c GL_OES_compressed_ETC1_RGB8_texture extension is supported
+    and the ETC1 texture has been encapsulated in the PVR container format.
+    Also, textures in the PVRTC2 and PVRTC4 formats can be loaded
+    if the \c GL_IMG_texture_compression_pvrtc extension is supported.
 
     \sa deleteTexture()
 */
 
 GLuint QGLContext::bindTexture(const QString &fileName)
 {
-    if (!qt_glCompressedTexImage2DARB) {
-        qWarning("QGLContext::bindTexture(): The GL implementation does not support texture"
-                 "compression extensions.");
-        return 0;
-    }
-
-    QGLDDSCache::const_iterator it = qgl_dds_cache()->constFind(fileName);
-    if (it != qgl_dds_cache()->constEnd()) {
+    Q_D(QGLContext);
+    QGLDDSCache *dds_cache = &(d->group->m_dds_cache);
+    QGLDDSCache::const_iterator it = dds_cache->constFind(fileName);
+    if (it != dds_cache->constEnd()) {
         glBindTexture(GL_TEXTURE_2D, it.value());
         return it.value();
     }
 
-    QFile f(fileName);
-    f.open(QIODevice::ReadOnly);
-
-    char tag[4];
-    f.read(&tag[0], 4);
-    if (strncmp(tag,"DDS ", 4) != 0) {
-        qWarning("QGLContext::bindTexture(): not a DDS image file.");
-        return 0;
-    }
-
-    DDSFormat ddsHeader;
-    f.read((char *) &ddsHeader, sizeof(DDSFormat));
-
-    if (!ddsHeader.dwLinearSize) {
-        qWarning("QGLContext::bindTexture() DDS image size is not valid.");
-        return 0;
-    }
-
-    int factor = 4;
-    int bufferSize = 0;
-    int blockSize = 16;
-    GLenum format;
-
-    switch(ddsHeader.ddsPixelFormat.dwFourCC) {
-    case FOURCC_DXT1:
-        format = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
-        factor = 2;
-        blockSize = 8;
-        break;
-    case FOURCC_DXT3:
-        format = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
-        break;
-    case FOURCC_DXT5:
-        format = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
-        break;
-    default:
-        qWarning("QGLContext::bindTexture() DDS image format not supported.");
+    QGLTexture texture(this);
+    QSize size = texture.bindCompressedTexture(fileName);
+    if (!size.isValid())
         return 0;
-    }
-
-    if (ddsHeader.dwMipMapCount > 1)
-        bufferSize = ddsHeader.dwLinearSize * factor;
-    else
-        bufferSize = ddsHeader.dwLinearSize;
-
-    GLubyte *pixels = (GLubyte *) malloc(bufferSize*sizeof(GLubyte));
-    f.seek(ddsHeader.dwSize + 4);
-    f.read((char *) pixels, bufferSize);
-    f.close();
-
-    GLuint tx_id;
-    glGenTextures(1, &tx_id);
-    glBindTexture(GL_TEXTURE_2D, tx_id);
-    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-
-    int size;
-    int offset = 0;
-    int w = ddsHeader.dwWidth;
-    int h = ddsHeader.dwHeight;
 
-    // load mip-maps
-    for(int i = 0; i < (int) ddsHeader.dwMipMapCount; ++i) {
-        if (w == 0) w = 1;
-        if (h == 0) h = 1;
-
-        size = ((w+3)/4) * ((h+3)/4) * blockSize;
-        qt_glCompressedTexImage2DARB(GL_TEXTURE_2D, i, format, w, h, 0,
-                                     size, pixels + offset);
-        offset += size;
-
-        // half size for each mip-map level
-        w = w/2;
-        h = h/2;
-    }
-
-    free(pixels);
-
-    qgl_dds_cache()->insert(fileName, tx_id);
-    return tx_id;
+    dds_cache->insert(fileName, texture.id);
+    return texture.id;
 }
 
 static inline QRgb qt_gl_convertToGLFormatHelper(QRgb src_pixel, GLenum texture_format)
@@ -2593,17 +2505,20 @@ GLuint QGLContext::bindTexture(const QPixmap &pixmap, QMacCompatGLenum target, Q
 */
 void QGLContext::deleteTexture(GLuint id)
 {
+    Q_D(QGLContext);
+
     if (QGLTextureCache::instance()->remove(this, id))
         return;
 
     // check the DDS cache if the texture wasn't found in the pixmap/image
     // cache
-    QList<QString> ddsKeys = qgl_dds_cache()->keys();
+    QGLDDSCache *dds_cache = &(d->group->m_dds_cache);
+    QList<QString> ddsKeys = dds_cache->keys();
     for (int i = 0; i < ddsKeys.size(); ++i) {
-        GLuint texture = qgl_dds_cache()->value(ddsKeys.at(i));
+        GLuint texture = dds_cache->value(ddsKeys.at(i));
         if (id == texture) {
             glDeleteTextures(1, &texture);
-            qgl_dds_cache()->remove(ddsKeys.at(i));
+            dds_cache->remove(ddsKeys.at(i));
             return;
         }
     }
@@ -4907,8 +4822,14 @@ void QGLExtensions::init_extensions()
         glExtensions |= SampleBuffers;
     if (extensions.contains("GL_SGIS_generate_mipmap"))
         glExtensions |= GenerateMipmap;
-    if (extensions.contains("GL_EXT_texture_compression_s3tc"))
+    if (extensions.contains("GL_ARB_texture_compression"))
         glExtensions |= TextureCompression;
+    if (extensions.contains("GL_EXT_texture_compression_s3tc"))
+        glExtensions |= DDSTextureCompression;
+    if (extensions.contains("GL_OES_compressed_ETC1_RGB8_texture"))
+        glExtensions |= ETC1TextureCompression;
+    if (extensions.contains("GL_IMG_texture_compression_pvrtc"))
+        glExtensions |= PVRTCTextureCompression;
     if (extensions.contains("GL_ARB_fragment_program"))
         glExtensions |= FragmentProgram;
     if (extensions.contains("GL_ARB_texture_mirrored_repeat"))
@@ -4951,12 +4872,6 @@ void QGLExtensions::init_extensions()
 
     if (extensions.contains("GL_EXT_bgra"))
         glExtensions |= BGRATextureFormat;
-
-
-    QGLContext cx(QGLFormat::defaultFormat());
-    if (glExtensions & TextureCompression) {
-        qt_glCompressedTexImage2DARB = (pfn_glCompressedTexImage2DARB) cx.getProcAddress(QLatin1String("glCompressedTexImage2DARB"));
-    }
 }
 
 /*
@@ -5112,4 +5027,340 @@ void QGLSharedResourceGuard::setContext(const QGLContext *context)
     }
 }
 
+QSize QGLTexture::bindCompressedTexture
+    (const QString& fileName, const char *format)
+{
+    QFile file(fileName);
+    if (!file.open(QIODevice::ReadOnly))
+        return QSize();
+    QByteArray contents = file.readAll();
+    file.close();
+    return bindCompressedTexture
+        (contents.constData(), contents.size(), format);
+}
+
+// PVR header format for container files that store textures compressed
+// with the ETC1, PVRTC2, and PVRTC4 encodings.  Format information from the
+// PowerVR SDK at http://www.imgtec.com/powervr/insider/powervr-sdk.asp
+// "PVRTexTool Reference Manual, version 1.11f".
+struct PvrHeader
+{
+    quint32 headerSize;
+    quint32 height;
+    quint32 width;
+    quint32 mipMapCount;
+    quint32 flags;
+    quint32 dataSize;
+    quint32 bitsPerPixel;
+    quint32 redMask;
+    quint32 greenMask;
+    quint32 blueMask;
+    quint32 alphaMask;
+    quint32 magic;
+    quint32 surfaceCount;
+};
+
+#define PVR_MAGIC               0x21525650      // "PVR!" in little-endian
+
+#define PVR_FORMAT_MASK         0x000000FF
+#define PVR_FORMAT_PVRTC2       0x00000018
+#define PVR_FORMAT_PVRTC4       0x00000019
+#define PVR_FORMAT_ETC1         0x00000036
+
+#define PVR_HAS_MIPMAPS         0x00000100
+#define PVR_TWIDDLED            0x00000200
+#define PVR_NORMAL_MAP          0x00000400
+#define PVR_BORDER_ADDED        0x00000800
+#define PVR_CUBE_MAP            0x00001000
+#define PVR_FALSE_COLOR_MIPMAPS 0x00002000
+#define PVR_VOLUME_TEXTURE      0x00004000
+#define PVR_ALPHA_IN_TEXTURE    0x00008000
+#define PVR_VERTICAL_FLIP       0x00010000
+
+#ifndef GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG
+#define GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG      0x8C00
+#define GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG      0x8C01
+#define GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG     0x8C02
+#define GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG     0x8C03
+#endif
+
+#ifndef GL_ETC1_RGB8_OES
+#define GL_ETC1_RGB8_OES                        0x8D64
+#endif
+
+bool QGLTexture::canBindCompressedTexture
+    (const char *buf, int len, const char *format, bool *hasAlpha)
+{
+    if (QSysInfo::ByteOrder != QSysInfo::LittleEndian) {
+        // Compressed texture loading only supported on little-endian
+        // systems such as x86 and ARM at the moment.
+        return false;
+    }
+    if (!format) {
+        // Auto-detect the format from the header.
+        if (len >= 4 && !qstrncmp(buf, "DDS ", 4)) {
+            *hasAlpha = true;
+            return true;
+        } else if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4)) {
+            const PvrHeader *pvrHeader =
+                reinterpret_cast<const PvrHeader *>(buf);
+            *hasAlpha = (pvrHeader->alphaMask != 0);
+            return true;
+        }
+    } else {
+        // Validate the format against the header.
+        if (!qstricmp(format, "DDS")) {
+            if (len >= 4 && !qstrncmp(buf, "DDS ", 4)) {
+                *hasAlpha = true;
+                return true;
+            }
+        } else if (!qstricmp(format, "PVR") || !qstricmp(format, "ETC1")) {
+            if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4)) {
+                const PvrHeader *pvrHeader =
+                    reinterpret_cast<const PvrHeader *>(buf);
+                *hasAlpha = (pvrHeader->alphaMask != 0);
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+#define ctx QGLContext::currentContext()
+
+QSize QGLTexture::bindCompressedTexture
+    (const char *buf, int len, const char *format)
+{
+    if (QSysInfo::ByteOrder != QSysInfo::LittleEndian) {
+        // Compressed texture loading only supported on little-endian
+        // systems such as x86 and ARM at the moment.
+        return QSize();
+    }
+#if !defined(QT_OPENGL_ES)
+    if (!glCompressedTexImage2D) {
+        if (!(QGLExtensions::glExtensions & QGLExtensions::TextureCompression)) {
+            qWarning("QGLContext::bindTexture(): The GL implementation does "
+                     "not support texture compression extensions.");
+            return QSize();
+        }
+        glCompressedTexImage2D = (_glCompressedTexImage2DARB) ctx->getProcAddress(QLatin1String("glCompressedTexImage2DARB"));
+        if (!glCompressedTexImage2D) {
+            qWarning("QGLContext::bindTexture(): could not resolve "
+                     "glCompressedTexImage2DARB.");
+            return QSize();
+        }
+    }
+#endif
+    if (!format) {
+        // Auto-detect the format from the header.
+        if (len >= 4 && !qstrncmp(buf, "DDS ", 4))
+            return bindCompressedTextureDDS(buf, len);
+        else if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4))
+            return bindCompressedTexturePVR(buf, len);
+    } else {
+        // Validate the format against the header.
+        if (!qstricmp(format, "DDS")) {
+            if (len >= 4 && !qstrncmp(buf, "DDS ", 4))
+                return bindCompressedTextureDDS(buf, len);
+        } else if (!qstricmp(format, "PVR") || !qstricmp(format, "ETC1")) {
+            if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4))
+                return bindCompressedTexturePVR(buf, len);
+        }
+    }
+    return QSize();
+}
+
+QSize QGLTexture::bindCompressedTextureDDS(const char *buf, int len)
+{
+    // We only support 2D texture loading at present.
+    if (target != GL_TEXTURE_2D)
+        return QSize();
+
+    // Bail out if the necessary extension is not present.
+    if (!(QGLExtensions::glExtensions & QGLExtensions::DDSTextureCompression)) {
+        qWarning("QGLContext::bindTexture(): DDS texture compression is not supported.");
+        return QSize();
+    }
+
+    const DDSFormat *ddsHeader = reinterpret_cast<const DDSFormat *>(buf + 4);
+    if (!ddsHeader->dwLinearSize) {
+        qWarning("QGLContext::bindTexture(): DDS image size is not valid.");
+        return QSize();
+    }
+
+    int blockSize = 16;
+    GLenum format;
+
+    switch(ddsHeader->ddsPixelFormat.dwFourCC) {
+    case FOURCC_DXT1:
+        format = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
+        blockSize = 8;
+        break;
+    case FOURCC_DXT3:
+        format = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
+        break;
+    case FOURCC_DXT5:
+        format = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
+        break;
+    default:
+        qWarning("QGLContext::bindTexture(): DDS image format not supported.");
+        return QSize();
+    }
+
+    const GLubyte *pixels =
+        reinterpret_cast<const GLubyte *>(buf + ddsHeader->dwSize + 4);
+
+    glGenTextures(1, &id);
+    glBindTexture(GL_TEXTURE_2D, id);
+    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+
+    int size;
+    int offset = 0;
+    int available = len - int(ddsHeader->dwSize + 4);
+    int w = ddsHeader->dwWidth;
+    int h = ddsHeader->dwHeight;
+
+    // load mip-maps
+    for(int i = 0; i < (int) ddsHeader->dwMipMapCount; ++i) {
+        if (w == 0) w = 1;
+        if (h == 0) h = 1;
+
+        size = ((w+3)/4) * ((h+3)/4) * blockSize;
+        if (size > available)
+            break;
+        glCompressedTexImage2D(GL_TEXTURE_2D, i, format, w, h, 0,
+                               size, pixels + offset);
+        offset += size;
+        available -= size;
+
+        // half size for each mip-map level
+        w = w/2;
+        h = h/2;
+    }
+
+    // DDS images are not inverted.
+    options &= ~QGLContext::InvertedYBindOption;
+
+    return QSize(ddsHeader->dwWidth, ddsHeader->dwHeight);
+}
+
+QSize QGLTexture::bindCompressedTexturePVR(const char *buf, int len)
+{
+    // We only support 2D texture loading at present.  Cube maps later.
+    if (target != GL_TEXTURE_2D)
+        return QSize();
+
+    // Determine which texture format we will be loading.
+    const PvrHeader *pvrHeader = reinterpret_cast<const PvrHeader *>(buf);
+    GLenum textureFormat;
+    quint32 minWidth, minHeight;
+    switch (pvrHeader->flags & PVR_FORMAT_MASK) {
+    case PVR_FORMAT_PVRTC2:
+        if (pvrHeader->alphaMask)
+            textureFormat = GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG;
+        else
+            textureFormat = GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG;
+        minWidth = 16;
+        minHeight = 8;
+        break;
+
+    case PVR_FORMAT_PVRTC4:
+        if (pvrHeader->alphaMask)
+            textureFormat = GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG;
+        else
+            textureFormat = GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG;
+        minWidth = 8;
+        minHeight = 8;
+        break;
+
+    case PVR_FORMAT_ETC1:
+        textureFormat = GL_ETC1_RGB8_OES;
+        minWidth = 4;
+        minHeight = 4;
+        break;
+
+    default:
+        qWarning("QGLContext::bindTexture(): PVR image format 0x%x not supported.", int(pvrHeader->flags & PVR_FORMAT_MASK));
+        return QSize();
+    }
+
+    // Bail out if the necessary extension is not present.
+    if (textureFormat == GL_ETC1_RGB8_OES) {
+        if (!(QGLExtensions::glExtensions &
+                    QGLExtensions::ETC1TextureCompression)) {
+            qWarning("QGLContext::bindTexture(): ETC1 texture compression is not supported.");
+            return QSize();
+        }
+    } else {
+        if (!(QGLExtensions::glExtensions &
+                    QGLExtensions::PVRTCTextureCompression)) {
+            qWarning("QGLContext::bindTexture(): PVRTC texture compression is not supported.");
+            return QSize();
+        }
+    }
+
+    // Boundary check on the buffer size.
+    quint32 bufferSize = pvrHeader->headerSize + pvrHeader->dataSize;
+    if (bufferSize > quint32(len)) {
+        qWarning("QGLContext::bindTexture(): PVR image size is not valid.");
+        return QSize();
+    }
+
+    // Create the texture.
+    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+    glGenTextures(1, &id);
+    glBindTexture(GL_TEXTURE_2D, id);
+    if (pvrHeader->mipMapCount) {
+        if ((options & QGLContext::LinearFilteringBindOption) != 0) {
+            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
+        } else {
+            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);
+        }
+    } else if ((options & QGLContext::LinearFilteringBindOption) != 0) {
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    } else {
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    }
+
+    // Load the compressed mipmap levels.
+    const GLubyte *buffer =
+        reinterpret_cast<const GLubyte *>(buf + pvrHeader->headerSize);
+    bufferSize = pvrHeader->dataSize;
+    quint32 level = 0;
+    quint32 width = pvrHeader->width;
+    quint32 height = pvrHeader->height;
+    while (bufferSize > 0 && level < pvrHeader->mipMapCount) {
+        quint32 size =
+            (qMax(width, minWidth) * qMax(height, minHeight) *
+             pvrHeader->bitsPerPixel) / 8;
+        if (size > bufferSize)
+            break;
+        glCompressedTexImage2D(GL_TEXTURE_2D, GLint(level), textureFormat,
+                               GLsizei(width), GLsizei(height), 0,
+                               GLsizei(size), buffer);
+        width /= 2;
+        height /= 2;
+        buffer += size;
+        ++level;
+    }
+
+    // Restore the default pixel alignment for later texture uploads.
+    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
+
+    // Set the invert flag for the texture.
+    if ((pvrHeader->flags & PVR_VERTICAL_FLIP) != 0)
+        options |= QGLContext::InvertedYBindOption;
+    else
+        options &= ~QGLContext::InvertedYBindOption;
+
+    return QSize(pvrHeader->width, pvrHeader->height);
+}
+
+#undef ctx
+
 QT_END_NAMESPACE
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index b2407ba..0f785a5 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -222,6 +222,8 @@ public:
 class QGLContextResource;
 class QGLSharedResourceGuard;
 
+typedef QHash<QString, GLuint> QGLDDSCache;
+
 // QGLContextPrivate has the responsibility of creating context groups.
 // QGLContextPrivate and QGLShareRegister will both maintain the reference counter and destroy
 // context groups when needed.
@@ -246,6 +248,7 @@ private:
     QHash<QGLContextResource *, void *> m_resources;
     QGLSharedResourceGuard *m_guards; // double-linked list of active guards.
     QAtomicInt m_refs;
+    QGLDDSCache m_dds_cache;
 
     void cleanupResources(const QGLContext *ctx);
 
@@ -377,7 +380,10 @@ public:
         PixelBufferObject       = 0x00000800,
         FramebufferBlit         = 0x00001000,
         NPOTTextures            = 0x00002000,
-        BGRATextureFormat       = 0x00004000
+        BGRATextureFormat       = 0x00004000,
+        DDSTextureCompression   = 0x00008000,
+        ETC1TextureCompression  = 0x00010000,
+        PVRTCTextureCompression = 0x00020000
     };
     Q_DECLARE_FLAGS(Extensions, Extension)
 
@@ -482,6 +488,14 @@ public:
     QPixmapData* boundPixmap;
 #endif
 
+    bool canBindCompressedTexture
+        (const char *buf, int len, const char *format, bool *hasAlpha);
+    QSize bindCompressedTexture
+        (const QString& fileName, const char *format = 0);
+    QSize bindCompressedTexture
+        (const char *buf, int len, const char *format = 0);
+    QSize bindCompressedTextureDDS(const char *buf, int len);
+    QSize bindCompressedTexturePVR(const char *buf, int len);
 };
 
 class QGLTextureCache {
diff --git a/src/opengl/qglextensions_p.h b/src/opengl/qglextensions_p.h
index 3510765..62e216c 100644
--- a/src/opengl/qglextensions_p.h
+++ b/src/opengl/qglextensions_p.h
@@ -184,6 +184,10 @@ typedef void (APIENTRY *_glBlitFramebufferEXT) (int srcX0, int srcY0, int srcX1,
 typedef void (APIENTRY *_glRenderbufferStorageMultisampleEXT) (GLenum target, GLsizei samples,
                                                                GLenum internalformat, GLsizei width, GLsizei height);
 
+// ARB_texture_compression
+typedef void (APIENTRY *_glCompressedTexImage2DARB) (GLenum, GLint, GLenum, GLsizei,
+                                                     GLsizei, GLint, GLsizei, const GLvoid *);
+
 QT_BEGIN_NAMESPACE
 
 struct QGLExtensionFuncs
@@ -289,6 +293,11 @@ struct QGLExtensionFuncs
 #endif
         qt_glMapBufferARB = 0;
         qt_glUnmapBufferARB = 0;
+
+#if !defined(QT_OPENGL_ES)
+        // Texture compression
+        qt_glCompressedTexImage2DARB = 0;
+#endif
     }
 
 
@@ -397,6 +406,10 @@ struct QGLExtensionFuncs
     _glMapBufferARB qt_glMapBufferARB;
     _glUnmapBufferARB qt_glUnmapBufferARB;
 
+#if !defined(QT_OPENGL_ES)
+    // Texture compression
+    _glCompressedTexImage2DARB qt_glCompressedTexImage2DARB;
+#endif
 };
 
 
@@ -732,6 +745,10 @@ struct QGLExtensionFuncs
 #define glClearDepth glClearDepthf
 #endif
 
+#if !defined(QT_OPENGL_ES)
+#define glCompressedTexImage2D QGLContextPrivate::extensionFuncs(ctx).qt_glCompressedTexImage2DARB
+#endif
+
 extern bool qt_resolve_framebufferobject_extensions(QGLContext *ctx);
 bool qt_resolve_buffer_extensions(QGLContext *ctx);
 
diff --git a/src/opengl/qpixmapdata_gl.cpp b/src/opengl/qpixmapdata_gl.cpp
index ab17789..0299cea 100644
--- a/src/opengl/qpixmapdata_gl.cpp
+++ b/src/opengl/qpixmapdata_gl.cpp
@@ -53,6 +53,8 @@
 #include <private/qpaintengineex_opengl2_p.h>
 
 #include <qdesktopwidget.h>
+#include <qfile.h>
+#include <qimagereader.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -407,6 +409,61 @@ void QGLPixmapData::fromImage(const QImage &image,
     }
 }
 
+bool QGLPixmapData::fromFile(const QString &filename, const char *format,
+                             Qt::ImageConversionFlags flags)
+{
+    if (pixelType() == QPixmapData::BitmapType)
+        return QPixmapData::fromFile(filename, format, flags);
+    QFile file(filename);
+    if (!file.open(QIODevice::ReadOnly))
+        return false;
+    QByteArray data = file.peek(64);
+    bool alpha;
+    if (m_texture.canBindCompressedTexture
+            (data.constData(), data.size(), format, &alpha)) {
+        resize(0, 0);
+        data = file.readAll();
+        file.close();
+        QSize size = m_texture.bindCompressedTexture
+            (data.constData(), data.size(), format);
+        if (!size.isEmpty()) {
+            w = size.width();
+            h = size.height();
+            is_null = false;
+            d = 32;
+            m_hasAlpha = alpha;
+            m_source = QImage();
+            m_dirty = isValid();
+            return true;
+        }
+        return false;
+    }
+    fromImage(QImageReader(&file, format).read(), flags);
+    return !isNull();
+}
+
+bool QGLPixmapData::fromData(const uchar *buffer, uint len, const char *format,
+                             Qt::ImageConversionFlags flags)
+{
+    bool alpha;
+    const char *buf = reinterpret_cast<const char *>(buffer);
+    if (m_texture.canBindCompressedTexture(buf, int(len), format, &alpha)) {
+        resize(0, 0);
+        QSize size = m_texture.bindCompressedTexture(buf, int(len), format);
+        if (!size.isEmpty()) {
+            w = size.width();
+            h = size.height();
+            is_null = false;
+            d = 32;
+            m_hasAlpha = alpha;
+            m_source = QImage();
+            m_dirty = isValid();
+            return true;
+        }
+    }
+    return QPixmapData::fromData(buffer, len, format, flags);
+}
+
 bool QGLPixmapData::scroll(int dx, int dy, const QRect &rect)
 {
     Q_UNUSED(dx);
diff --git a/src/opengl/qpixmapdata_gl_p.h b/src/opengl/qpixmapdata_gl_p.h
index 8a13e03..007c52a 100644
--- a/src/opengl/qpixmapdata_gl_p.h
+++ b/src/opengl/qpixmapdata_gl_p.h
@@ -106,6 +106,10 @@ public:
     // Re-implemented from QPixmapData:
     void resize(int width, int height);
     void fromImage(const QImage &image, Qt::ImageConversionFlags flags);
+    bool fromFile(const QString &filename, const char *format,
+                  Qt::ImageConversionFlags flags);
+    bool fromData(const uchar *buffer, uint len, const char *format,
+                  Qt::ImageConversionFlags flags);
     void copy(const QPixmapData *data, const QRect &rect);
     bool scroll(int dx, int dy, const QRect &rect);
     void fill(const QColor &color);