[FFmpeg-devel] [PATCH] PC Paintbrush PCX decoder

[Michael Niedermayer]

On Tue, Dec 25, 2007 at 01:45:06PM +0100, Ivo wrote:
> Hi,
> 
> Here's a decoder for PC Paintbrush PCX files.
> 
> http://wiki.multimedia.cx/index.php?title=PCX
> 
> Samples are uploaded to:
> 
> http://samples.mplayerhq.hu/MPlayer/incoming/pcx
> 
> Merry christmas,
> --Ivo

[...]

> +typedef struct PCXContext {
> +    AVFrame picture;
> +} PCXContext;
> +
> +static int pcx_init(AVCodecContext *avctx) {
> +    PCXContext *s = avctx->priv_data;
> +
> +    avcodec_get_frame_defaults((AVFrame*)&s->picture);
> +    avctx->coded_frame= (AVFrame*)&s->picture;

what are these casts doing?


> +    s->picture.data[0] = NULL;

why?


[...]

> +static void pcx_ega_palette(uint8_t *src, uint32_t *dst) {
> +    int i;
> +
> +    for (i=0; i<16; i++, dst++, src+=3)
> +        *dst = (src[0]<<16) + (src[1]<<8) + src[2];

*dst++ = bytestream_get_be24(&src);


> +    memset(dst, 0, 240 * 4);

s/4/sizeof(*dst)/


[...]
> +            for (x=0, b=0; x<w*3; x+=3, b++) {
> +                ptr[x  ] = scanline[b                    ];
> +                ptr[x+1] = scanline[b+ bytes_per_line    ];
> +                ptr[x+2] = scanline[b+(bytes_per_line<<1)];
> +            }

for (x=0; x<w; x++) {
    ptr[3*x  ] = scanline[x                    ];
    ptr[3*x+1] = scanline[x+ bytes_per_line    ];
    ptr[3*x+2] = scanline[x+(bytes_per_line<<1)];
}


> +
> +            ptr += stride;
> +        }
> +
> +    } else if (nplanes == 1 && bits_per_pixel == 8) {
[...]
> +        for (y=0; y<256; y++, ptr+=4, buf+=3)
> +            *(uint32_t *)ptr = (buf[0]<<16) + (buf[1]<<8) + buf[2];

duplicate of pcx_ega_palette()

and pcx_ega_palette() can be factored out of the 3 if()


> +
> +    } else if (nplanes == 1) {   /* all packed formats, max. 16 colors */
> +        static const char params[3][4] = { {3,2,1}, {7,3,1}, {1,3,15} };
> +        uint8_t scanline[bytes_per_scanline];
> +        int i = bits_per_pixel == 4 ? 2 : bits_per_pixel-1;

> +        int d = params[0][i], m = params[1][i], n = params[2][i];
> +
> +        for (y=0; y<h; y++) {
> +            buf = pcx_rle_decode(buf, scanline, bytes_per_scanline, 0);
> +
> +            for (x=0; x<w; x++) {
> +                int v = scanline[x>>d], s = (m-(x&m)) * bits_per_pixel;
> +                ptr[x] = (v>>s) & n;
> +            }

get_bits()



> +            ptr += stride;
> +        }
> +
> +        pcx_ega_palette(bufstart+16, (uint32_t *) p->data[1]);
> +
> +    } else {    /* planar, 4, 8 or 16 colors */
> +        uint8_t scanline[bytes_per_scanline];
> +        int i, m;
> +
> +        for (y=0; y<h; y++) {
> +            buf = pcx_rle_decode(buf, scanline, bytes_per_scanline, 0);
> +
> +            m = 0x80;
> +            for (x=0; x<w; x++) {
> +                int v = 0;
> +                for (i=nplanes - 1; i>=0; i--) {
> +                    v <<= 1;
> +                    v  += !!(scanline[i*bytes_per_line + (x>>3)] & m);
> +                }
> +                ptr[x] = v;
> +                m >>= 1;
> +                m += !m * 0x80;
> +            }

for (x=0; x<w; x++) {
    int m= 0x80 >> (x&7);
    for (i=nplanes - 1; i>=0; i--)
        put_bits1(pb, !!(scanline[i*bytes_per_line + (x>>3)] & m));
}

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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