Draw Text on jpeg image from buffer

[mesut...@toros.edu.tr]

Hi, I'm new to skia. I need some answers and a short sample code if possible. I need to write an application to ip camera. I can get the video from cameray in "yuv" and "jpeg" format. I need to write text on the image. 

Before l was try opencv but because of high cpu usage l decide change library. 

my ip camera has arm neon processor and my application will run over ip camera.

how can I do this fastest? what way l must follow? 

video information structure

typedef struct {

     char * buff;

     char * frameTime;

     int size;

     int width;

     int height;

}

thanks for help.

[Hal Canary]

Skia can read and write jpeg files, assuming you link in libjpeg-turbo when you build.

Skia will convert to RGB to draw the image. 

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[mesut...@toros.edu.tr]

thank you for quick answer. yes l did build with my minimal needs for ubuntu x86 like this.

bin/gn gen out/x86 --args='is_official_build=false is_debug=false cc="clang" cxx="clang++" target_cpu="x86" target_os="linux" skia_use_libwebp=false skia_use_fontconfig=false skia_use_system_freetype2=false skia_use_egl=false skia_use_lua=false skia_use_libpng=false skia_use_vulkan=false skia_enable_pdf=false skia_use_sfntly=false skia_enable_tools=false skia_use_angle=false skia_use_dng_sdk=false'

when l finish my code l will compile for arm and build my code. 

l try write my code but l thinks some tings wrong, l try read jpeg data and writ text over it , for test trying l write to file jpeg file is 0 kb.

void drawText(void* pData)

{

VIDEO_EVENT* vidEvent;

        vidData = (VIDEO_EVENT*) pData;

sk_sp<SkData> data = SkData::MakeWithCString(pData->buff);

sk_sp<SkImage> img = SkImage::MakeFromEncoded(data);

SkBitmap bitmap;

bitmap.setInfo(SkImageInfo::Make(pData->width, pData->height, kRGBA_8888_SkColorType, kOpaque_SkAlphaType),0);

SkCanvas canvas(bitmap);

canvas.drawImage(img, 100, 50);

SkPaint paint;

SkString string("hello");

canvas.drawString(string, 20, 20, paint);

sk_sp<SkData> encoded = SkEncodeBitmap(bitmap, SkEncodedImageFormat::kJPEG, 100);

// l need put back jpeg data to pData->buff and set pData->size

// for test l write image to file but its write 0 kb.

FILE* pFile = fopen("/home/user/pics/j19.jpg", "wb+");

    if (!pFile) {

  fprintf(stderr, "The file '%s' was not opened\n", "j17.jpg");

  return;

    }

    fwrite(encoded->data(), encoded->size(), 1, pFile);

    fclose(pFile);

}

[Hal Canary]

#include <cassert>

#include <cstdio>

#include "SkCanvas.h"

#include "SkData.h"

#include "SkImage.h"

#include "SkSurface.h"

sk_sp<SkData> drawText(const void* jpegData, size_t jpegDataLen, const char* string) {

    assert(jpegDataLen);

    sk_sp<SkImage> img = SkImage::MakeFromEncoded(

            SkData::MakeWithoutCopy(jpegData, jpegDataLen));

    assert(img);

    sk_sp<SkSurface> surf = SkSurface::MakeRasterN32Premul(

            img->width() + 100, img->height() + 50);

    SkCanvas* canvas = surf->getCanvas();

    canvas->clear(SK_ColorWHITE);

    canvas->drawImage(img, 100, 50);

    SkPaint paint;

    canvas.drawString(string, 20, 20, paint);

    return surf->makeImageSnapshot()->encodeToData(SkEncodedImageFormat::kJPEG, 100);

}

void writeFile(SkData* src, const char* path) {

    FILE* pFile = fopen(path, "wb");

    if (!pFile) {

        fprintf(stderr, "The file '%s' was not opened\n", path);

        return;

    }

    fwrite(src->data(), src->size(), 1, pFile);

    fclose(pFile);

}

void test(VIDEO_EVENT* pData) {

    sk_sp<SkData> encoded = drawText(pData->buff, pData->size, "hello");

    assert(encoded);

    writeFile(encoded.get(), "/home/user/pics/j19.jpg");

}

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[mesut...@toros.edu.tr]

this sample code has helped me a lot, thank you very much

2 Mayıs 2018 Çarşamba 05:28:25 UTC+3 tarihinde Hal Canary yazdı:

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