Re: [PATCH] jpeg image reader

[Marco Gerards <mgerards@xs4all.nl>]

Bean <bean123ch@gmail.com> writes:

> On Jan 14, 2008 2:31 AM, Marco Gerards <mgerards@xs4all.nl> wrote:
>> > /*
>> >  *  GRUB  --  GRand Unified Bootloader
>> >  *  Copyright (C) 2008  Free Software Foundation, Inc.
>>
>> Did you write all the code yourself?
>
> yes, but i take some code segment from Independent JPEG Group's
> implementation, such as idct transformation and ycrcb -> rgb
> conversion.

I do not think these algorithms can be copyrighted and are in the
public domain?  Can you check this?

Colorspace convertion can be easily done.  I might even have some self
written code for this.  As for the IDCT, I could do that too, if it is
problematic?

> please remind me if something is left out.

I don't see anything you missed.  Please see this last comment below.

> static grub_err_t
> grub_jpeg_decode_sof (struct grub_jpeg_data *data)
> {
>   int i, cc;
>   grub_uint32_t next_marker;
>
>   next_marker = data->file->offset;
>   next_marker += grub_jpeg_get_word (data);
>
>   if (grub_jpeg_get_byte (data) != 8)
>     return grub_error (GRUB_ERR_BAD_FILE_TYPE,
> 		       "jpeg: only 8-bit precision is supported");
>
>   data->image_height = grub_jpeg_get_word (data);
>   data->image_width = grub_jpeg_get_word (data);
>
>   if ((!data->image_height) || (!data->image_width))
>     return grub_error (GRUB_ERR_BAD_FILE_TYPE, "jpeg: invalid image size");
>
>   cc = grub_jpeg_get_byte (data);
>   if (cc != 3)
>     return grub_error (GRUB_ERR_BAD_FILE_TYPE,
> 		       "jpeg: component count must be 3");
>
>   for (i = 0; i < cc; i++)
>     {
>       int id, ss;
>
>       id = grub_jpeg_get_byte (data) - 1;
>       if ((id < 0) || (id >= 3))
> 	return grub_error (GRUB_ERR_BAD_FILE_TYPE, "jpeg: invalid index");
>
>       ss = grub_jpeg_get_byte (data);	/* sampling factor  */
>       if (!id)
> 	{
> 	  data->vs = ss & 0xF;	/* vertical sampling  */
> 	  data->hs = ss >> 4;	/* horizontal sampling  */

Please use correct interpunction.

--
Marco