FBO and glReadPixels()

This topic contains 2 replies, has 2 voices, and was last updated by  PenCyot3 6 years, 3 months ago.

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  • #30584

    PenCyot3
    Member

    Correct pixel values were not acquired by glReadPixels() from framebuffer object.

    At first I cleared a color buffer with (1.0, 1.0, 1.0, 1.0) as follows.

      glBindFramebuffer( GL_FRAMEBUFFER, framebuffer );
      glClearColor( 1.0f, 1.0f, 1.0f, 1.0f );
      glClear( GL_COLOR_BUFFER_BIT );
      glBindFramebuffer( GL_FRAMEBUFFER, 0 );

    I took out pixel values by glReadPixels() as follows next.

      glBindFramebuffer( GL_FRAMEBUFFER, framebuffer );
      glPixelStorei( GL_PACK_ALIGNMENT, 1 );
      const int WIDTH  = 64;
      const int HEIGHT = 1;
      GLubyte pixels[4 * WIDTH * HEIGHT];
      glReadPixels( 0, 0, WIDTH, HEIGHT, GL_RGBA, GL_UNSIGNED_BYTE, pixels );
      glBindFramebuffer( GL_FRAMEBUFFER, 0 );

    All the elements of pixels should have been 0xFF then, but actually got the following values.

      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

    I tested it in Galaxy S (SC-02B Android 2.3.3 GINGERBREAD.OMKE3).

    source code: (md5sum=d1b861da715b9890745f6d004c679a4e)
     http://dl.dropbox.com/u/23346852/ticket-701_4/Test701_4-source.zip

    APK file: (md5sum=83432dab7d9556e55ab83cb6d401abea)
     http://dl.dropbox.com/u/23346852/ticket-701_4/Test701_4.apk

    Screenshot (Galaxy S)
    Galaxy%20S

    Screenshot (GALAPAGOS 003SH)

    #35007

    Hi,

    did you find a solution for this?

    Best Regards,

    Nicolas

    #35008

    PenCyot3
    Member

    Hi,

    Unfortunately I do not yet find this solution. Pinch

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