Implement support for 16bpc image formats

Adds support for 16bit per color image formats in QImage. This makes it
possible to read and write 16bpc PNGs, and take full advantage of the
16bpc paint engine.

[ChangeLog][QtGui][QImage] QImage now supports 64bit image formats with
16 bits per color channel, compatible with 16bpc PNG or RGBA16 OpenGL
formats.

Task-number: QTBUG-45858
Change-Id: Icd28bd5868a6efcf65cb5bd56031d42941e04099
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 75 insertions, 4 deletions

diff --git a/tests/auto/gui/qopengl/tst_qopengl.cpp b/tests/auto/gui/qopengl/tst_qopengl.cpp
index 5b1af9b6c9..f1360b9efe 100644
--- a/tests/auto/gui/qopengl/tst_qopengl.cpp
+++ b/tests/auto/gui/qopengl/tst_qopengl.cpp
@@ -82,6 +82,8 @@ private slots:
     void fboRendering();
     void fboRenderingRGB30_data();
     void fboRenderingRGB30();
+    void fboRenderingRGB64_data();
+    void fboRenderingRGB64();
     void fboHandleNulledAfterContextDestroyed();
     void fboMRT();
     void fboMRT_differentFormats();
@@ -614,6 +616,10 @@ void tst_QOpenGL::fboRenderingRGB30_data()
 #define GL_RGB10_A2                       0x8059
 #endif
 
+#ifndef GL_RGBA16
+#define GL_RGBA16                         0x805B
+#endif
+
 #ifndef GL_FRAMEBUFFER_RENDERABLE
 #define GL_FRAMEBUFFER_RENDERABLE         0x8289
 #endif
@@ -622,7 +628,7 @@ void tst_QOpenGL::fboRenderingRGB30_data()
 #define GL_FULL_SUPPORT                   0x82B7
 #endif
 
-static bool hasRGB10A2(QOpenGLContext *ctx)
+static bool supportsInternalFboFormat(QOpenGLContext *ctx, int glFormat)
 {
     if (ctx->format().majorVersion() < 3)
         return false;
@@ -631,7 +637,7 @@ static bool hasRGB10A2(QOpenGLContext *ctx)
         GLint value = -1;
         QOpenGLFunctions_4_2_Core* vFuncs = ctx->versionFunctions<QOpenGLFunctions_4_2_Core>();
         if (vFuncs && vFuncs->initializeOpenGLFunctions()) {
-            vFuncs->glGetInternalformativ(GL_TEXTURE_2D, GL_RGB10_A2, GL_FRAMEBUFFER_RENDERABLE, 1, &value);
+            vFuncs->glGetInternalformativ(GL_TEXTURE_2D, glFormat, GL_FRAMEBUFFER_RENDERABLE, 1, &value);
             if (value != GL_FULL_SUPPORT)
                 return false;
         }
@@ -657,7 +663,7 @@ void tst_QOpenGL::fboRenderingRGB30()
     if (!QOpenGLFramebufferObject::hasOpenGLFramebufferObjects())
         QSKIP("QOpenGLFramebufferObject not supported on this platform");
 
-    if (!hasRGB10A2(&ctx))
+    if (!supportsInternalFboFormat(&ctx, GL_RGB10_A2))
         QSKIP("An internal RGB30_A2 format is not guaranteed on this platform");
 
     // No multisample with combined depth/stencil attachment:
@@ -713,6 +719,71 @@ void tst_QOpenGL::fboRenderingRGB30()
     QVERIFY(((pixel >> 20) & 0x3f) > 0);
 }
 
+void tst_QOpenGL::fboRenderingRGB64_data()
+{
+    common_data();
+}
+
+void tst_QOpenGL::fboRenderingRGB64()
+{
+#if defined(Q_OS_LINUX) && defined(Q_CC_GNU) && !defined(__x86_64__)
+    QSKIP("QTBUG-22617");
+#endif
+
+    QFETCH(int, surfaceClass);
+    QScopedPointer<QSurface> surface(createSurface(surfaceClass));
+
+    QOpenGLContext ctx;
+    QVERIFY(ctx.create());
+
+    QVERIFY(ctx.makeCurrent(surface.data()));
+
+    if (!QOpenGLFramebufferObject::hasOpenGLFramebufferObjects())
+        QSKIP("QOpenGLFramebufferObject not supported on this platform");
+
+    if (!supportsInternalFboFormat(&ctx, GL_RGBA16))
+        QSKIP("An internal RGBA16 format is not guaranteed on this platform");
+
+    // No multisample with combined depth/stencil attachment:
+    QOpenGLFramebufferObjectFormat fboFormat;
+    fboFormat.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
+    fboFormat.setInternalTextureFormat(GL_RGBA16);
+
+    // Uncomplicate things by using POT:
+    const QSize size(256, 128);
+    QOpenGLFramebufferObject fbo(size, fboFormat);
+
+    if (fbo.attachment() != QOpenGLFramebufferObject::CombinedDepthStencil)
+        QSKIP("FBOs missing combined depth~stencil support");
+
+    QVERIFY(fbo.bind());
+
+    QPainter fboPainter;
+    QOpenGLPaintDevice device(fbo.width(), fbo.height());
+    bool painterBegun = fboPainter.begin(&device);
+    QVERIFY(painterBegun);
+
+    qt_opengl_draw_test_pattern(&fboPainter, fbo.width(), fbo.height());
+
+    fboPainter.end();
+
+    QImage fb = fbo.toImage();
+    QCOMPARE(fb.format(), QImage::Format_RGBA64_Premultiplied);
+    QCOMPARE(fb.size(), size);
+
+    qt_opengl_check_test_pattern(fb);
+
+    // Check rendering can handle precise 16 bit color values.
+    fboPainter.begin(&device);
+    fboPainter.fillRect(QRect(0, 0, 256, 128), QColor::fromRgba64(5, 1002, 8001, 65535));
+    fboPainter.end();
+    fb = fbo.toImage();
+    QRgba64 pixel = ((QRgba64*)fb.bits())[0];
+    QCOMPARE(pixel.red(), 5);
+    QCOMPARE(pixel.green(), 1002);
+    QCOMPARE(pixel.blue(), 8001);
+}
+
 void tst_QOpenGL::fboHandleNulledAfterContextDestroyed()
 {
     QWindow window;
@@ -844,7 +915,7 @@ void tst_QOpenGL::fboMRT_differentFormats()
     if (!f->hasOpenGLFeature(QOpenGLFunctions::MultipleRenderTargets))
         QSKIP("Multiple render targets not supported on this platform");
 
-    if (!hasRGB10A2(&ctx))
+    if (!supportsInternalFboFormat(&ctx, GL_RGB10_A2))
         QSKIP("RGB10_A2 not supported on this platform");
 
     // 3 color attachments, same size, different internal format, depth/stencil.