Re: [PATCH 1/2] stkutil: convert img to xpm

[Denis Kenzior <denkenz@gmail.com>]

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Hi Kristen,

On 07/22/2010 07:10 PM, Kristen Carlson Accardi wrote:
> ---
>  src/stkutil.c |  148 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  src/stkutil.h |    8 +++
>  2 files changed, 156 insertions(+), 0 deletions(-)
> 
> diff --git a/src/stkutil.c b/src/stkutil.c
> index 9cac850..46ae026 100644
> --- a/src/stkutil.c
> +++ b/src/stkutil.c
> @@ -6076,3 +6076,151 @@ char *stk_text_to_html(const char *utf8,
>  	/* return characters from string. Caller must free char data */
>  	return g_string_free(string, FALSE);
>  }
> +
> +static const char chars_table[] = {
> +	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C',
> +	'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
> +	'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c',
> +	'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
> +	'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '+', '.' };
> +
> +char *stk_image_to_xpm(const unsigned char *img, unsigned int len,
> +			enum stk_img_scheme scheme)
> +{
> +	guint8 width, height;
> +	unsigned int ncolors, nbits, entry, cpp;
> +	unsigned int i, j;
> +	int bit, k;
> +	unsigned short clut_offset = 0;
> +	guint8 *clut;
> +	GString *xpm;
> +	unsigned int pos = 0;
> +	const char xpm_header[] = "/* XPM */\n";
> +	const char declaration[] = "static char *xpm[] = {\n";
> +	char c[3];
> +
> +	if (img == NULL)
> +		return NULL;
> +
> +	/* sanity check length */
> +	if (len < 3)
> +		return NULL;
> +
> +	width = img[pos++];
> +	height = img[pos++];
> +
> +	if (scheme == STK_IMG_SCHEME_BASIC) {
> +		nbits = 1;
> +		ncolors = 2;
> +
> +		if (pos + ((width * height)/8) > len)
> +			return NULL;

You probably want (pos + (width * height + 7) / 8) > len here.  Also,
please keep doc/coding-style.txt Section M3 in mind here.

> +	} else {
> +		/* sanity check length */
> +		if (pos + 4 > len)
> +			return NULL;
> +
> +		nbits = img[pos++];
> +		ncolors = img[pos++];
> +
> +		/* the value of zero should be interpreted as 256 */
> +		if (ncolors == 0)
> +			ncolors = 256;
> +
> +		clut_offset = img[pos++] << 8;
> +		clut_offset |= img[pos++];
> +
> +		if ((clut_offset + (ncolors * 3) > len) ||
> +			(pos + (width * height * nbits)/8) > clut_offset)

Please keep in mind doc/coding-style.txt Section M4.  Sometimes it is
better to separate the || conditions into two separate ifs to satisfy
this rule.

Also, you're off by 1 again here.  You probably want (width * height *
nbits + 7) / 8.

This also brings up another point.  You're assuming that the caller is
appending the CLUT right after the image data and massaging the clut
offset appropriately.  This is a really bad idea since the caller will
have to do some significant pre-processing.

You can handle this in one of two ways:

1. Assume the calling logic will read the entire image file before
calling this function.  In this case, modifying the signature as follows
might be a good idea:

char *stk_image_to_xpm(const unsigned char *file,
			unsigned short file_len,
			enum stk_img_scheme scheme,
			unsigned short img_offset,
			unsigned short img_len);

2. Assume the calling logic is clever and will optimize reading of the
file, including peeking into the image header to determine the where the
CLUT is located and reading it.  In this case you can either reuse the
signature from 1 above, or come up with something else.

Remember, reading from the SIM is extremely slow, so any and all clever
optimization tricks are definitely wanted.

> +			return NULL;
> +	}
> +
> +	/* determine the number of chars need to represent the pixel */
> +	cpp = ncolors > 64 ? 2 : 1;
> +
> +	/*
> +	 * space needed:
> +	 * 	header line
> +	 *	declaration and beginning of assignment line
> +	 *	values - max length of 19
> +	 *	colors - ncolors * (cpp + whitespace + deliminators + color)
> +	 *	pixels - width * height * cpp + height deliminators "",\n
> +	 *	end of assignment - 2 chars "};"
> +	 */
> +	xpm = g_string_sized_new(strlen(xpm_header) + strlen(declaration) +
> +				19 + ((cpp + 14) * ncolors) +
> +				(width * height * cpp) + (4 * height) + 2);
> +	if (xpm == NULL)
> +		return NULL;
> +
> +	/* add header, declaration, values */
> +	g_string_append(xpm, xpm_header);
> +	g_string_append(xpm, declaration);
> +	g_string_append_printf(xpm, "\"%d %d %d %d\",\n", width, height,
> +				ncolors, cpp);
> +
> +	/* create colors */
> +	if (scheme == STK_IMG_SCHEME_BASIC) {
> +		g_string_append(xpm, "\"0\tc #000000\",\n");
> +		g_string_append(xpm, "\"1\tc #FFFFFF\",\n");
> +	} else {
> +		clut = (guint8 *) &img[clut_offset];
> +
> +		for (i = 0; i < ncolors; i++) {
> +			/* lookup char representation of this number */
> +			if (ncolors > 64) {
> +				c[0] = chars_table[i / 64];
> +				c[1] = chars_table[i % 64];
> +				c[2] = '\0';
> +			} else {
> +				c[0] = chars_table[i % 64];
> +				c[1] = '\0';
> +			}
> +
> +			if ((i == (ncolors - 1)) &&
> +					scheme == STK_IMG_SCHEME_TRANSPARENCY)
> +				g_string_append_printf(xpm,
> +					"\"%s\tc None\",\n", c);
> +			else
> +				g_string_append_printf(xpm,
> +					"\"%s\tc #%02hhX%02hhX%02hhX\",\n",
> +					c, clut[0], clut[1], clut[2]);
> +			clut += 3;
> +		}
> +	}
> +
> +	/* height rows of width pixels */
> +	k = 7;
> +	for (i = 0; i < height; i++) {
> +		g_string_append(xpm, "\"");
> +		for (j = 0; j < width; j++) {
> +			entry = 0;
> +			for (bit = nbits - 1; bit >= 0; bit--) {
> +				entry |= (img[pos] >> k & 0x1) << bit;
> +				k--;
> +
> +				/* see if we crossed a byte boundary */
> +				if (k < 0) {
> +					k = 7;
> +					pos++;
> +				}
> +			}
> +
> +			/* lookup char representation of this number */
> +			if (ncolors > 64) {
> +				c[0] = chars_table[entry / 64];
> +				c[1] = chars_table[entry % 64];
> +				c[2] = '\0';
> +			} else {
> +				c[0] = chars_table[entry % 64];
> +				c[1] = '\0';
> +			}

There should be an empty line here

> +			g_string_append_printf(xpm, "%s", c);
> +		}

And another empty line here.

> +		g_string_append(xpm, "\",\n");
> +	}

And another empty line here.

> +	g_string_append(xpm, "};");
> +
> +	/* Caller must free char data */
> +	return g_string_free(xpm, FALSE);
> +}
> diff --git a/src/stkutil.h b/src/stkutil.h
> index 1fbd68b..1e33a65 100644
> --- a/src/stkutil.h
> +++ b/src/stkutil.h
> @@ -557,6 +557,12 @@ enum stk_me_status {
>  	STK_ME_STATUS_NOT_IDLE = 	0x01
>  };
>  
> +enum stk_img_scheme {
> +	STK_IMG_SCHEME_BASIC =		0x11,
> +	STK_IMG_SCHEME_COLOR =		0x21,
> +	STK_IMG_SCHEME_TRANSPARENCY =	0x22,
> +};
> +
>  /* For data object that only has a byte array with undetermined length */
>  struct stk_common_byte_array {
>  	unsigned char *array;
> @@ -1644,3 +1650,5 @@ const unsigned char *stk_pdu_from_envelope(const struct stk_envelope *envelope,
>  						unsigned int *out_length);
>  char *stk_text_to_html(const char *text,
>  				const unsigned short *attrs, int num_attrs);
> +char *stk_image_to_xpm(const unsigned char *img, unsigned int len,
> +			enum stk_img_scheme scheme);

Regards,
-Denis