VGLite draw text example

[Flo1989]

Hi,

i try to use the VGlite in an FreeRTOS application. I can display and prozess raster pictures without problems. But now i want to use the "vg_lite_draw_text" function to write a text. I do not find any documentation how to use it.

When i understand the code in a right Way i had to first register the font with "vg_lite_register_font". What i am missin here is how the structure of the "void *data" in vg_lite_font_params has to look like.

typedef struct vg_lite_font_params
{
    char name[MAX_FONT_NAME_LEN]; /*! font-family name */
    eFontType_t    font_type;     /*! Raster/Vector font */
    eFontWeight_t   font_weight;  /*! Font weight enum value */
    eFontStretch_t  font_stretch; /*! Font stretch enum value */
    eFontStyle_t    font_style;   /*! Font style enum value */
    int font_height;              /*! Font height in pixels */
    int data_len;                 /*! Font data buffer length */
    void *data; /*! the address where the actual font data is stored; it is the
                 * responsibility of the user/application to load it there */
} vg_lite_font_params_t;

Is there any documentation about this?

Best Regards,

Florian

[howard_liu]

@Flo1989 Hi Florian, 

To use VGLite draw text API, you must have a SVG file containing an embedded font. Please reference to the SVGTiny 1.2 for the embedded font in a SVG.

There is a vectorFontConverter tool that extracts font data from SVG files  and saves it in an intermediate data format known asVFT-VectorFont. Then it can be registered with the VGLite driver to enable applications to draw text. This tool will be released as one tool of VGLite toolkit soon.

[howardliu]

I attached an example to show how to use VGLite draw text API for your reference (Only passing IAR tool). The vectorFontConverter tool can be found from NXP.

Usage: vft_create  input_svg   output_vft

After creating a VFT file, you can use the xxd tool (Linux tool, available in the msys on windows) to create a header file:

xxd -i output_vft > output.h

[maglash64]

Thank you for this reply, was looking for the same for some time,

Can you also shed some light on why the vg_lite_prerspective() transform function was removed from the API? using it makes the GPU stop rendering.

[howard_liu]

Now vg_lite_get_transform_matrix() is used to create a perspective matrix. It's easier than vg_lite_prerspective().

[maglash64]

Hi, can you give an example on how to use vg_lite_get_transform_matrix() API function?

I used it the following way but it did nothing.

the image is stored in the vg_lite_buffer_t image_buffer and has size 256x256 and format VG_LITE_RGBX8888,

target buffer rt is the main frame buffer.

vg_lite_point4_t src={0,0,256,256};
vg_lite_point4_t dst = {0,0,256,300};

vg_lite_identity(&matrix);

vg_lite_get_transform_matrix(src, dst, &matrix);

vg_lite_blit(&rt, &image_buffer, &matrix, VG_LITE_BLEND_MULTIPLY, 0, VG_LITE_FILTER_BI_LINEAR);

[howardliu]

@maglash64 You need to give 4-point location for src and 4-point location for dst. 

vg_lite_point4_t src={{x0, y0}, {x1, y1}, {x2, y2}, {x3, y3}};

You can reference to the code of VGLiteBlit under boards\evkmimxrt1170\vglite_appnote_samples. Below's the download link:

https://www.nxp.com/docs/en/application-note-software/AN13075SW.zip

[Flo1989]

Hi,

sry but i have no access to that link.

Best Regards,

Florian

[joanxie]

this couldn't be shared on the public community, I will mail to you later

[svoulaz_ik]

Hello @joanxie ,

trying to access the link too, as we are interested in the offline tool to convert SVG to elementary structures - specifically for vector fonts. Also, a "VGLite Toolkit" is mentioned in AN13778, but I cannot find any resource. Could you help? Thanks in advance.

Stefano

[joanxie]

Pls refer to the link as below:

"https://community.nxp.com/t5/i-MX-RT1170-CAS-Training/GPU2D-Overview-and-VGLite-Library-PDF-and-Exam..."

[maglash64]

Hi, I am also facing a similar problem, did you find the solution? What is the format of font to be placed in memory?