Blog

1. Serialization and deserialization.
2. Decoding and Encoding of JPEG image.
3. Resizing.
4. Comparison, is it really the fastest solution?

Serialization/deserialization

DWORD dwBytesRead = 0;
HANDLE hFile = CreateFile(fileName.c_str(), GENERIC_READ, 
                                              FILE_SHARE_READ, NULL, 
                                              OPEN_EXISTING, 
                                              FILE_ATTRIBUTE_NORMAL, 
                                              NULL);

unsigned long size = GetFileSize(hFile, NULL);

data.resize(size);

ReadFile(hFile, (char*)(&(data)[0]), size, &dwBytesRead, NULL);

FILE* file = std::fopen(fileName.c_str(), "rb");

if (file)
{
    fseek(file, 0, SEEK_END);
    long size = ftell(file);
    rewind(file);
    data.resize(size);
    fread((char*)(&(data)[0]), 1, size, file);
    fclose(file);
}

bool JPEGImage::decode()
{
    int jpegSubsamp, ret;
    tjhandle jpegDecompressor = tjInitDecompress();

    ret = tjDecompressHeader2(jpegDecompressor, m_data->data(),
                              m_data->size(), &m_width, &m_height,
                              &jpegSubsamp);

    if (!ret)
    {
        unsigned long size = static_cast < unsigned long> (m_width *m_height * 3);
        m_buffer->resize(size);
        ret = tjDecompress2(jpegDecompressor, m_data->data(),
                            m_data->size(), m_buffer->data(),
                            m_width, 0, m_height, 3,
                            TJFLAG_FASTDCT | TJFLAG_NOREALLOC);

        tjDestroy(jpegDecompressor);
    }

    return ret == 0;
}

__kernel void resize_nn(__read_only image2d_t source,
                        __write_only image2d_t dest,
                         struct SImage src_img, 
                         struct SImage dst_img, 
                         float ratioX, float ratioY)
{
    const int gx = get_global_id(0);
    const int gy = get_global_id(1);
    const int2 pos = { gx, gy };
	
    if (pos.x >= dst_img.Width || pos.y >= dst_img.Height)
        return;

	float2 srcpos = {(pos.x + 0.4995f) / ratioX, (pos.y + 0.4995f) / ratioY};
    int2 SrcSize = (int2)(src_img.Width, src_img.Height);
	float4 value;
    int2 ipos = convert_int2(srcpos);
        
    if (ipos.x< 0 || ipos.x >= SrcSize.x || ipos.y< 0 || ipos.y >= SrcSize.y)
        value = 0;
    else
        value = read_imagef(source, sampler, ipos);

    write_imagef(dest, pos, value);
}

Comparison

• OpenCL batch resizer
• Python imaging
• Imagemagick
• OpenCV (Python wrapper)
• Adobe Photoshop CS6 (win7)
• ACDSee 6.0 (win7)

Conclusion

References