[Spice-devel] [vdagent-win PATCH v11 4/6] Support encoding PNG images

[Christophe Fergeau]

Acked-by: Christophe Fergeau <cfergeau at redhat.com>

On Mon, Jul 24, 2017 at 01:10:24PM +0100, Frediano Ziglio wrote:
> Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> Acked-by: Christophe Fergeau <cfergeau at redhat.com>
> ---
>  vdagent/imagepng.cpp | 118 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 115 insertions(+), 3 deletions(-)
> 
> diff --git a/vdagent/imagepng.cpp b/vdagent/imagepng.cpp
> index f966cc2..d15f2a8 100644
> --- a/vdagent/imagepng.cpp
> +++ b/vdagent/imagepng.cpp
> @@ -19,6 +19,7 @@
>  
>  #include <png.h>
>  #include <algorithm>
> +#include <vector>
>  
>  #include "imagepng.h"
>  
> @@ -50,6 +51,43 @@ static void read_from_bufio(png_structp png, png_bytep out, png_size_t size)
>      io.pos += size;
>  }
>  
> +struct WriteBufferIo {
> +    uint8_t *buf;
> +    uint32_t pos, size;
> +    WriteBufferIo():
> +        buf(NULL), pos(0), size(0)
> +    {}
> +    ~WriteBufferIo() { free(buf); }
> +    uint8_t *release() {
> +        uint8_t *res = buf;
> +        buf = NULL;
> +        pos = size = 0;
> +        return res;
> +    }
> +};
> +
> +static void write_to_bufio(png_structp png, png_bytep in, png_size_t size)
> +{
> +    WriteBufferIo& io(*(WriteBufferIo*)png_get_io_ptr(png));
> +    if (io.pos + size > io.size) {
> +        uint32_t new_size = io.size ? io.size * 2 : 4096;
> +        while (io.pos + size >= new_size) {
> +            new_size *= 2;
> +        }
> +        uint8_t *p = (uint8_t*) realloc(io.buf, new_size);
> +        if (!p)
> +            png_error(png, "out of memory");
> +        io.buf = p;
> +        io.size = new_size;
> +    }
> +    memcpy(io.buf+io.pos, in, size);
> +    io.pos += size;
> +}
> +
> +static void flush_bufio(png_structp png)
> +{
> +}
> +
>  size_t PngCoder::get_dib_size(const uint8_t *data, size_t size)
>  {
>      return convert_to_dib(NULL, data, size);
> @@ -226,10 +264,84 @@ void PngCoder::get_dib_data(uint8_t *dib, const uint8_t *data, size_t size)
>      convert_to_dib(dib, data, size);
>  }
>  
> -uint8_t *PngCoder::from_bitmap(const BITMAPINFO& info, const void *bits, long &size)
> +uint8_t *PngCoder::from_bitmap(const BITMAPINFO& bmp_info, const void *bits, long &size)
>  {
> -    // TODO not implemented
> -    return NULL;
> +    // this vector is here to avoid leaking resources if libpng use setjmp/longjmp
> +    std::vector<png_color> palette;
> +    WriteBufferIo io;
> +
> +    png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
> +    if (!png)
> +        return 0;
> +
> +    png_infop info = png_create_info_struct(png);
> +    if (!info) {
> +        png_destroy_write_struct(&png, &info);
> +        return 0;
> +    }
> +
> +    if (setjmp(png_jmpbuf(png))) {
> +        png_destroy_write_struct(&png, &info);
> +        return 0;
> +    }
> +
> +    png_set_write_fn(png, &io, write_to_bufio, flush_bufio);
> +
> +    const BITMAPINFOHEADER& head(bmp_info.bmiHeader);
> +    int color_type;
> +    int out_bits = head.biBitCount;
> +    switch (out_bits) {
> +    case 1:
> +    case 4:
> +    case 8:
> +        color_type = PNG_COLOR_TYPE_PALETTE;
> +        break;
> +    case 24:
> +    case 32:
> +        png_set_bgr(png);
> +        color_type = PNG_COLOR_TYPE_RGB;
> +        break;
> +    default:
> +        png_error(png, "BMP bit count not supported");
> +        break;
> +    }
> +    // TODO detect gray
> +    png_set_IHDR(png, info, head.biWidth, head.biHeight,
> +                 out_bits > 8 ? 8 : out_bits, color_type,
> +                 PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
> +                 PNG_FILTER_TYPE_DEFAULT);
> +
> +    // palette
> +    if (color_type == PNG_COLOR_TYPE_PALETTE) {
> +        palette.resize(head.biClrUsed);
> +        const RGBQUAD *rgb = bmp_info.bmiColors;
> +        for (unsigned int color = 0; color < head.biClrUsed; ++color) {
> +            palette[color].red = rgb->rgbRed;
> +            palette[color].green = rgb->rgbGreen;
> +            palette[color].blue = rgb->rgbBlue;
> +            ++rgb;
> +        }
> +        png_set_PLTE(png, info, &palette[0], palette.size());
> +    }
> +
> +    png_write_info(png, info);
> +
> +    const unsigned int width = head.biWidth;
> +    const unsigned int height = head.biHeight;
> +    const size_t stride = compute_dib_stride(width, out_bits);
> +    const size_t image_size = stride * height;
> +
> +    // now do the actual conversion!
> +    const uint8_t *src = (const uint8_t*)bits + image_size;
> +    for (unsigned int row = 0; row < height; ++row) {
> +        src -= stride;
> +        png_write_row(png, src);
> +    }
> +    png_write_end(png, NULL);
> +
> +    png_destroy_write_struct(&png, &info);
> +    size = io.pos;
> +    return io.release();
>  }
>  
>  ImageCoder *create_png_coder()
> -- 
> 2.13.3
> 
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