mod_magick_interlace.c

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * The Apache mod_magick_interlace module provides a filter that sets the
 * interlace type of the image generated by mod_magick.
 *
 *  Author: Graham Leggett
 *
 * Basic configuration:
 *
 * <Location />
 *   <If "%{QUERY_STRING} =~ /./">
 *     SetOutputFilter MAGICK;MAGICK_INTERLACE
 *     MagickInterlace plane
 *   </If>
 * </Location>
 *
 * The MagickInterlace directive takes an expression containing the interlace
 * type to be used. Possible options are: none|line|plane|partition
 */

#include <apr_strings.h>

#include "httpd.h"
#include "http_config.h"
#include "http_log.h"
#include "ap_expr.h"
#include "util_filter.h"

#include "mod_magick.h"

module AP_MODULE_DECLARE_DATA magick_interlace_module;

#define DEFAULT_INTERLACE_TYPE PlaneInterlace

typedef struct magick_conf {
    int interlace_set:1; /* have the interlace been set */
    ap_expr_info_t *interlace;  /* resize to interlace */
} magick_conf;

static void *create_magick_dir_config(apr_pool_t *p, char *dummy)
{
    magick_conf *new = (magick_conf *) apr_pcalloc(p, sizeof(magick_conf));

    return (void *) new;
}

static void *merge_magick_dir_config(apr_pool_t *p, void *basev, void *addv)
{
    magick_conf *new = (magick_conf *) apr_pcalloc(p, sizeof(magick_conf));
    magick_conf *add = (magick_conf *) addv;
    magick_conf *base = (magick_conf *) basev;

    new->interlace = (add->interlace_set == 0) ? base->interlace : add->interlace;
    new->interlace_set = add->interlace_set || base->interlace_set;

    return new;
}

static const char *set_magick_interlace(cmd_parms *cmd, void *dconf, const char *arg)
{
    magick_conf *conf = dconf;
    const char *expr_err = NULL;

    conf->interlace = ap_expr_parse_cmd(cmd, arg, AP_EXPR_FLAG_STRING_RESULT,
            &expr_err, NULL);

    if (expr_err) {
        return apr_pstrcat(cmd->temp_pool,
                "Cannot parse expression '", arg, "': ",
                expr_err, NULL);
    }

    conf->interlace_set = 1;

    return NULL;
}

static const command_rec magick_cmds[] = {
    AP_INIT_TAKE1("MagickInterlace", set_magick_interlace, NULL, ACCESS_CONF | OR_ALL,
        "Set the interlace type used to render the image. Must be one of none|line|plane|partition"
        ), { NULL },
};

static InterlaceType magick_parse_interlace_type(const char *interlace_type)
{

    switch (interlace_type[0]) {
    case 'n': {
        if (!strcmp(interlace_type, "none")) {
            return NoInterlace;
        }
        break;
    }
    case 'l': {
        if (!strcmp(interlace_type, "line")) {
            return LineInterlace;
        }
        break;
    }
    case 'p': {
        if (!strcmp(interlace_type, "plane")) {
            return PlaneInterlace;
        }
        else if (!strcmp(interlace_type, "partition")) {
            return PartitionInterlace;
        }
        break;
    }
    }

    return UndefinedInterlace;
}

static apr_status_t magick_interlace_out_filter(ap_filter_t *f, apr_bucket_brigade *bb)
{
    apr_bucket *e;

    for (e = APR_BRIGADE_FIRST(bb);
         e != APR_BRIGADE_SENTINEL(bb);
         e = APR_BUCKET_NEXT(e))
    {

        /* EOS means we are done. */
        if (APR_BUCKET_IS_EOS(e)) {
            ap_remove_output_filter(f);
            break;
        }

        /* Magick bucket? */
        if (AP_BUCKET_IS_MAGICK(e)) {

            magick_conf *conf = ap_get_module_config(f->r->per_dir_config,
                    &magick_interlace_module);

            ap_bucket_magick *m = e->data;

            InterlaceType interlace = DEFAULT_INTERLACE_TYPE;

            if (conf->interlace) {
                const char *err = NULL, *str;

                str = ap_expr_str_exec(f->r, conf->interlace, &err);
                if (err) {
                    ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, f->r,
                                    "Failure while evaluating the interlace type expression for '%s', "
                                    "interlace ignored: %s", f->r->uri, err);
                }
                else {
                    interlace = magick_parse_interlace_type(str);
                    if (interlace == UndefinedInterlace) {
                        ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, f->r,
                                      "Interlace type for '%s' of '%s' not recognised, "
                                      "must be one of none|line|plane|partition"
                                      ", using 'plane'", f->r->uri, str);
                    }
                }
            }

            if (!MagickSetInterlaceScheme(m->wand, interlace)) {
                char *description;
                ExceptionType severity;

                description = MagickGetException(m->wand, &severity);
                ap_log_rerror(APLOG_MARK, APLOG_ERR, APR_EGENERAL, f->r,
                        "MagickSetInterlaceScheme: %s (severity %d)", description,
                        severity);
                MagickRelinquishMemory(description);

                return APR_EGENERAL;
            }

        }

    }

    return ap_pass_brigade(f->next, bb);
}


static void register_hooks(apr_pool_t *p)
{
    ap_register_output_filter("MAGICK_INTERLACE", magick_interlace_out_filter, NULL,
            AP_FTYPE_CONTENT_SET);
}

AP_DECLARE_MODULE(magick_interlace) =
{
    STANDARD20_MODULE_STUFF,
    create_magick_dir_config, /* dir config creater */
    merge_magick_dir_config,  /* dir merger --- default is to override */
    NULL,                     /* server config */
    NULL,                     /* merge server config */
    magick_cmds,              /* command apr_table_t */
    register_hooks            /* register hooks */
};