enable/disable local alpha and global alpha -blog archive

[max_tsai]

To enable local alpha needs 32 bpp within bootargs, like "video=mxcdi1fb:RGB666,XGA,bpp=32"

Attached a simple code to enable/disable local/global alpha bledding by ioctl below.

alpha blending

[saurabh206]

Hi,

Max

Where is the attachment?

[max_tsai]

The attachment is broken. Attached the code below.

---

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <sys/ioctl.h>

#include <unistd.h>

//#include <asm/arch/mxcfb.h>

#define MXCFB_SET_GBL_ALPHA _IOW('F', 0x21, struct mxcfb_gbl_alpha)

#define MXCFB_SET_CLR_KEY _IOW('F', 0x22, struct mxcfb_color_key)

#define MXCFB_SET_LOC_ALPHA _IOWR('F', 0x26, struct mxcfb_loc_alpha)

struct mxcfb_gbl_alpha {

        int enable;

        int alpha;

};

struct mxcfb_color_key {

        int enable;

        __u32 color_key;

};

struct mxcfb_loc_alpha {

        int enable;

        int alpha_in_pixel;                 

        unsigned long alpha_phy_addr0;      

        unsigned long alpha_phy_addr1;      

};

int main(int argc, char **argv)

{

        int fb_fd;

        struct mxcfb_gbl_alpha gbl_alpha;

    struct mxcfb_loc_alpha l_alpha;

    struct mxcfb_color_key key;

    char fbname[128];

    char *endptr;

        if(argc < 3){

               printf("Usage: %s fb_chn [gn|ln] [alpha_val[0-255]] [color_key[0x00000000-0xffffffff]]\n",argv[0]);

               return -1;

        }

    memset(fbname, 0, sizeof(fbname));

    sprintf(fbname, "/dev/graphics/fb%s", argv[1]);

    printf("open '%s'\n", fbname);

        fb_fd = open(fbname,O_RDWR,0);

    if (fb_fd == -1) {

        perror("open");

        exit(1);

    }

    if (argv[2][0] == 'g') {

        gbl_alpha.enable = 1;

        gbl_alpha.alpha = atoi(argv[3]);

        if (ioctl(fb_fd, MXCFB_SET_GBL_ALPHA, &gbl_alpha))

            perror("ioctl");

        if (argv[2][1] == '1') {

            printf("enable global alpha blending\n");

            key.enable = 1;

        } else {

            printf("disable global alpha blending\n");

            key.enable = 0;

        }

        key.color_key = strtol(argv[4], &endptr, 16);

        printf("key = 0x%x\n", key.color_key);

        if (ioctl(fb_fd, MXCFB_SET_CLR_KEY, &key))

            perror("ioctl");

    } else if (argv[2][0] =='l') {

        if (argv[2][1] == '1') {

            l_alpha.enable = 1;

            printf("enable local alpha blending\n");

        } else {

            l_alpha.enable = 0;

            printf("disable local alpha blending\n");

        }

        l_alpha.alpha_in_pixel = 1;

        if (ioctl(fb_fd, MXCFB_SET_LOC_ALPHA, &l_alpha))

            perror("ioctl");

    }

        close(fb_fd);

        return 0;

}

[saurabh206]

Hi,

Max

Thanks for sharing the code.

Our setup  is like data from android surface flinger is available "/dev/graphics/fb0"

We want to do overlay with CSI buffer which is written on "/dev/graphics/fb1"

We are able to get it working with global alpha and colour keying. But due to some limitation with our GUI we can not use global alpha.

But If I disable global alpha and enable the local alpha than data from /dev/graphics/fb1 is not display.

- Is it possible to do alpha blending using local alpha without colour keying?

- What is a significance of alpha_phy_addr0, alpha_phy_addr1 and alpha_in_pixel?

Thanks

Saurabh

[max_tsai]

hi Your data going to show into framebuffer must include alpha information(ARGB), so the pixel size of framebuffer should be 32bpp.

alpha_in_pixel means each pixel embedds alpha channel, and alpha_phy_addr are the buffers used by IPU.

[max_tsai]

BTW, color key should work with global alpha. IPU get alpha info from each pixel for local alpha, and color key doesn't mater for local alpha. you can refer to "hardware/mx5x/libgralloc/framebuffer.cpp".

[saurabh206]

Hi,

Max

Thanks for the valuable information.

Our fame buffer is 32bit and it should contain ARGB format. I will verify this.

"hardware/imx/mx5x/libgralloc/framebuffer.cpp" will be used for imx6q.

To enable local alpha I need to build source code without "HAVE_FSL_EPDC_FB".

Can you please explain that what is significance of HAVE_FSL_EPDC_FB?

- Saurabh

[max_tsai]

hi I trace FSL ICS and FSL JB, "HAVE_FSL_EPDC_FB" "hardware/imx/mx6/libgralloc_wrapper/Android.mk" is marked.

Also alpha blending configuration should not be related with this flag.

[saurabh206]

Hi,

I have modified the frame buffer code to pass alpha channel.

hardware\imx\mx6\libgralloc_wrapper\framebuffer.cpp

        info.bits_per_pixel = 32;

        info.red.offset     = 8;     

        info.red.length     = 8;

        info.green.offset   = 16;

        info.green.length   = 8;

        info.blue.offset    = 24;

        info.blue.length    = 8;

        info.transp.offset  = 0;

        info.transp.length  = 8;  //We need local alpha transparency

And I am enabling the local alpha channel by following code.

int set_local_alpha()
{
   struct mxcfb_loc_alpha loc_alpha;
   int fd_fb;

   if ((fd_fb = open("/dev/graphics/fb0", O_RDWR, 0)) < 0)
   {
       __android_log_print(ANDROID_LOG_DEBUG,CF_TAG,"unable to open /dev/graphics/fb0 ");
       return 0;
   }

loc_alpha.alpha_in_pixel = 0;
loc_alpha.enable = 1;
   loc_alpha.alpha_phy_addr0=0;
   loc_alpha.alpha_phy_addr1=0;

if ( ioctl(fd_fb, MXCFB_SET_LOC_ALPHA, &loc_alpha) < 0) {
       __android_log_print(ANDROID_LOG_DEBUG,CF_TAG,"Error in applying Local Alpha\n");
}
   close (fd_fb);
  
}

After setting the local alpha I got only blue screen on display, no Android UI or not CSI content.

Do you have idea, what part is missing?

[max_tsai]

loc_alpha.alpha_in_pixel should be 1 to indicate there is alpha information per each pixel.

[saurabh206]

HI,

Max

I got it working.

Thanks for your support.

loc_alpha.alpha_in_pixel = 1;

loc_alpha.enable = 1;

   loc_alpha.alpha_phy_addr0=0;

   loc_alpha.alpha_phy_addr1=0;

if ( ioctl(fd_fb, MXCFB_SET_LOC_ALPHA, &loc_alpha) < 0) {
       __android_log_print(ANDROID_LOG_DEBUG,CF_TAG,"Error in applying Local Alpha\n");
}

Is required to get local alpha working.

Thanks

Saurabh

[LeonardoSandova]

Actually seems that is not an attachment, it is a link but the link is broken MaxTsai.