Qt Embedded交换颜色位:红色和蓝色

Question

我在ARM显示设备上使用QtEmbedded(4.8.0),帧缓冲区(/ dev/fb0)上的颜色深度为16位.在这种情况下,我们将颜色位RED和BLUE交换.

我们使用以下编译标志:

./configure -embedded arm -xplatform qws/linux-arm-gnueabi-g++ -prefix /home/rchaves/Toolchain -release -opensource -shared -fast -depths 16 -largefile -no-exceptions -no-accessibility -stl -no-sql-mysql -no-sql-psql -no-sql-oci -no-sql-odbc -no-sql-tds -no-sql-db2 -no-sql-sqlite -no-sql-sqlite2 -no-sql-ibase -no-qt3support -no-xmlpatterns -no-multimedia -no-audio-backend -no-phonon-backend -no-svg -no-webkit -no-javascript-jit -no-script -no-scripttools -no-declarative -no-declarative-debug -qt-zlib -qt-libtiff -qt-libpng -qt-libmng -qt-libjpeg -no-openssl -no-nis -no-cups -iconv -no-pch -no-dbus -qt-freetype -no-opengl -qt-gfx-linuxfb -qt-kbd-linuxinput -qt-mouse-tslib -nomake demos -nomake examples

以及执行应用程序的以下参数:

QWS_DISPLAY=LinuxFb:/dev/fb0:depth=16 ./app -qws

这里有应用程序framebuffer(samples)日志:

The framebuffer device was opened successfully.

Fixed screen info:
    id:          DISP3 BG
    smem_start:  0x93800000
    smem_len:    7864320
    type:        0
    type_aux:    0
    visual:      2
    xpanstep:    1
    ypanstep:    1
    ywrapstep:   0
    line_length: 2048
    mmio_start:  0x0
    mmio_len:    0
    accel:       0

The framebuffer device was mapped to memory successfully.

Successfully switched to graphics mode.

Variable screen info:
    xres:           1024
    yres:           768
    xres_virtual:   1024
    yres_virtual:   3840
    yoffset:        0
    xoffset:        0
    bits_per_pixel: 16
    grayscale: 0
    red:    offset:  0, length:  5, msb_right:  0
    green:  offset:  5, length:  6, msb_right:  0
    blue:   offset: 11, length:  5, msb_right:  0
    transp: offset:  0, length:  0, msb_right:  0
    nonstd:       0
    activate:     64
    height:       -1
    width:        -1
    accel_flags:  0x0
    pixclock:     15385
    left_margin:  157
    right_margin: 157
    upper_margin: 16
    lower_margin: 15
    hsync_len:    5
    vsync_len:    1
    sync:         0
    vmode:        0

Frame Buffer Performance test...
    Average:   43020 usecs
    Bandwidth: 174.338 MByte/Sec
    Max. FPS:  23.245 fps

Will draw 3 rectangles on the screen,
they should be colored red, green and blue (in that order).
Done.

Answer 1

迟到总比不到好。我在使用 Qt5.5.1 和 linuxfb 插件的 SAM5 处理器上遇到了这个问题。重新配置或重新编译 Qt5 框架无法解决问题。

显然LinuxFB插件不支持BGR格式。有一个开放的错误跟踪此问题。检查determineFormat中的函数../src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp，您会发现无论提供哪种类型的帧缓冲区信息，ImageFormat 都被硬编码为 **RGB。

要解决该问题，应用该错误附带的补丁可能会帮助您解决此问题。

我说“可能”是因为我的帧缓冲区驱动程序错误地报告它是 RBG 格式。所以要小心。如果是这种情况，只需对swapRgb标志进行硬编码，直到修复帧缓冲区驱动程序为止。