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jbig2dec: Handle non-nominal adaptive pixel locations in template 1.

Optimized generic region decoders can only handle nominal
adaptive pixel locations, while the unoptimized generic region
decoders can handle them being located at any location.

Previously the optimized decode was always used regardless of the
locations of the adaptive pixels, possibly causing decoding
issues. Now an unoptimized decoder is added for template 1 and is
being used whenever the adaptive pixel locations are at non-nominal
locations.

--- a/jbig2_generic.c

+++ b/jbig2_generic.c

@@ -167,6 +167,49 @@

 }

 static int

+jbig2_decode_generic_template1_unopt(Jbig2Ctx *ctx,

+                                     Jbig2Segment *segment,

+                                     const Jbig2GenericRegionParams *params, Jbig2ArithState *as, Jbig2Image *image, Jbig2ArithCx *GB_stats)

+{

+    const int GBW = image->width;

+    const int GBH = image->height;

+    uint32_t CONTEXT;

+    int x, y;

+    bool bit;

+    int code = 0;

+

+    if (pixel_outside_field(params->gbat[0], params->gbat[1]))

+        return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number,

+                           "adaptive template pixel is out of field");

+

+    /* this version is generic and easy to understand, but very slow */

+

+    for (y = 0; y < GBH; y++) {

+        for (x = 0; x < GBW; x++) {

+            CONTEXT = 0;

+            CONTEXT |= jbig2_image_get_pixel(image, x - 1, y) << 0;

+            CONTEXT |= jbig2_image_get_pixel(image, x - 2, y) << 1;

+            CONTEXT |= jbig2_image_get_pixel(image, x - 3, y) << 2;

+            CONTEXT |= jbig2_image_get_pixel(image, x + params->gbat[0], y + params->gbat[1]) << 3;

+            CONTEXT |= jbig2_image_get_pixel(image, x + 2, y - 1) << 4;

+            CONTEXT |= jbig2_image_get_pixel(image, x + 1, y - 1) << 5;

+            CONTEXT |= jbig2_image_get_pixel(image, x + 0, y - 1) << 6;

+            CONTEXT |= jbig2_image_get_pixel(image, x - 1, y - 1) << 7;

+            CONTEXT |= jbig2_image_get_pixel(image, x - 2, y - 1) << 8;

+            CONTEXT |= jbig2_image_get_pixel(image, x + 2, y - 2) << 9;

+            CONTEXT |= jbig2_image_get_pixel(image, x + 1, y - 2) << 10;

+            CONTEXT |= jbig2_image_get_pixel(image, x + 0, y - 2) << 11;

+            CONTEXT |= jbig2_image_get_pixel(image, x - 1, y - 2) << 12;

+            bit = jbig2_arith_decode(as, &GB_stats[CONTEXT], &code);

+            if (code)

+                return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, -1, "failed to decode arithmetic code when handling generic template0");

+            jbig2_image_set_pixel(image, x, y, bit);

+        }

+    }

+    return 0;

+}

+

+static int

 jbig2_decode_generic_template1(Jbig2Ctx *ctx,

                                Jbig2Segment *segment,

                                const Jbig2GenericRegionParams *params, Jbig2ArithState *as, Jbig2Image *image, Jbig2ArithCx *GB_stats)

@@ -178,9 +221,6 @@

     byte *gbreg_line = (byte *) image->data;

     int code = 0;

-    /* todo: currently we only handle the nominal gbat location */

-    /* when resolved make sure to call jbig2_check_adaptive_pixel_in_field() */

-

 #ifdef OUTPUT_PBM

     printf("P4\n%d %d\n", GBW, GBH);

 #endif

@@ -725,8 +765,12 @@

             return jbig2_decode_generic_template0(ctx, segment, params, as, image, GB_stats);

         else

             return jbig2_decode_generic_template0_unopt(ctx, segment, params, as, image, GB_stats);

-    } else if (!params->MMR && params->GBTEMPLATE == 1)

-        return jbig2_decode_generic_template1(ctx, segment, params, as, image, GB_stats);

+    } else if (!params->MMR && params->GBTEMPLATE == 1) {

+        if (gbat[0] == +3 && gbat[1] == -1)

+            return jbig2_decode_generic_template1(ctx, segment, params, as, image, GB_stats);

+        else

+            return jbig2_decode_generic_template1_unopt(ctx, segment, params, as, image, GB_stats);

+    }

     else if (!params->MMR && params->GBTEMPLATE == 2) {

         if (gbat[0] == 2 && gbat[1] == -1)

             return jbig2_decode_generic_template2a(ctx, segment, params, as, image, GB_stats);