terom@56: #include "png.h" // pt_png header
terom@56: #include "error.h"
terom@56: #include "shared/log.h" // debug only
terom@56: 
terom@56: #include <png.h> // sysmtem libpng header
terom@56: #include <assert.h>
terom@56: 
terom@56: 
terom@56: #define min(a, b) (((a) < (b)) ? (a) : (b))
terom@56: 
terom@69: int pt_png_check (const char *path)
terom@69: {
terom@69:     FILE *fp;
terom@69:     uint8_t header[8];
terom@69:     int ret;
terom@69: 
terom@69:     // fopen
terom@69:     if ((fp = fopen(path, "rb")) == NULL)
terom@69:         RETURN_ERROR(PT_ERR_IMG_OPEN);
terom@69: 
terom@69:     // read
terom@69:     if (fread(header, 1, sizeof(header), fp) != sizeof(header))
terom@69:         JUMP_SET_ERROR(ret, PT_ERR_IMG_FORMAT);
terom@69:       
terom@69:     // compare signature  
terom@69:     if (png_sig_cmp(header, 0, sizeof(header)))
terom@69:         // not a PNG file
terom@69:         ret = 1;
terom@69: 
terom@69:     else
terom@69:         // valid PNG file
terom@69:         ret = 0;
terom@69: 
terom@69: error:
terom@69:     // cleanup
terom@69:     fclose(fp);
terom@69: 
terom@69:     return ret;
terom@69: }
terom@69: 
terom@56: int pt_png_open (struct pt_image *image, struct pt_png_img *img)
terom@56: {
terom@56:     int err;
terom@69: 
terom@69:     // init
terom@69:     memset(img, 0, sizeof(*img));
terom@56:     
terom@56:     // open I/O
terom@69:     if ((err = pt_image_open_file(image, &img->fh)))
terom@56:         JUMP_ERROR(err);
terom@56: 
terom@56:     // create the struct
terom@56:     if ((img->png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL)) == NULL)
terom@56:         JUMP_SET_ERROR(err, PT_ERR_PNG_CREATE);
terom@56: 
terom@56:     // create the info
terom@56:     if ((img->info = png_create_info_struct(img->png)) == NULL)
terom@56:         JUMP_SET_ERROR(err, PT_ERR_PNG_CREATE);
terom@56: 
terom@56:     // setup error trap for the I/O
terom@56:     if (setjmp(png_jmpbuf(img->png)))
terom@56:         JUMP_SET_ERROR(err, PT_ERR_PNG);
terom@56:     
terom@56:     // setup error trap
terom@56:     if (setjmp(png_jmpbuf(img->png)))
terom@56:         JUMP_SET_ERROR(err, PT_ERR_PNG);
terom@56:     
terom@56: 
terom@56:     // setup I/O to FILE
terom@69:     png_init_io(img->png, img->fh);
terom@56: 
terom@56:     // read meta-info
terom@56:     png_read_info(img->png, img->info);
terom@56: 
terom@56: 
terom@69:     // img->fh will be closed by pt_png_release_read
terom@56:     return 0;
terom@56: 
terom@56: error:
terom@56:     // cleanup
terom@56:     pt_png_release_read(img);
terom@56:     
terom@56:     return err;
terom@56: }
terom@56: 
terom@56: int pt_png_read_header (struct pt_png_img *img, struct pt_png_header *header, size_t *data_size)
terom@56: {
terom@69:     // check image doesn't use any options we don't handle
terom@69:     if (png_get_interlace_type(img->png, img->info) != PNG_INTERLACE_NONE) {
terom@69:         log_warn("Can't handle interlaced PNG");
terom@69: 
terom@69:         RETURN_ERROR(PT_ERR_IMG_FORMAT);
terom@69:     }
terom@69: 
terom@56: 
terom@56:     // initialize
terom@56:     memset(header, 0, sizeof(*header));
terom@56: 
terom@56:     // fill in basic info
terom@56:     header->width = png_get_image_width(img->png, img->info);
terom@56:     header->height = png_get_image_height(img->png, img->info);
terom@56:     header->bit_depth = png_get_bit_depth(img->png, img->info);
terom@56:     header->color_type = png_get_color_type(img->png, img->info);
terom@56: 
terom@56:     log_debug("width=%u, height=%u, bit_depth=%u, color_type=%u", 
terom@56:             header->width, header->height, header->bit_depth, header->color_type
terom@56:     );
terom@56: 
terom@56:     // only pack 1 pixel per byte, changes rowbytes
terom@56:     if (header->bit_depth < 8)
terom@56:         png_set_packing(img->png);
terom@56: 
terom@56:     // fill in other info
terom@56:     header->row_bytes = png_get_rowbytes(img->png, img->info);
terom@56: 
terom@56:     // calculate bpp as num_channels * bpc
terom@69:     // this assumes the packed bit depth will be either 8 or 16
terom@56:     header->col_bytes = png_get_channels(img->png, img->info) * (header->bit_depth == 16 ? 2 : 1);
terom@56: 
terom@56:     log_debug("row_bytes=%u, col_bytes=%u", header->row_bytes, header->col_bytes);
terom@56:     
terom@56:     // palette etc.
terom@56:     if (header->color_type == PNG_COLOR_TYPE_PALETTE) {
terom@56:         int num_palette;
terom@56:         png_colorp palette;
terom@56: 
terom@56:         if (png_get_PLTE(img->png, img->info, &palette, &num_palette) == 0)
terom@69:             // PLTE chunk not read?
terom@56:             RETURN_ERROR(PT_ERR_PNG);
terom@56:         
terom@56:         // should only be 256 of them at most
terom@56:         assert(num_palette <= PNG_MAX_PALETTE_LENGTH);
terom@56:     
terom@56:         // copy
terom@56:         header->num_palette = num_palette;
terom@56:         memcpy(&header->palette, palette, num_palette * sizeof(*palette));
terom@56:         
terom@56:         log_debug("num_palette=%u", num_palette);
terom@56:     }
terom@56: 
terom@56:     // calculate data size
terom@56:     *data_size = header->height * header->row_bytes;
terom@56:     
terom@56:     return 0;
terom@56: }
terom@56: 
terom@56: /**
terom@56:  * Decode the PNG data directly to memory - not good for sparse backgrounds
terom@56:  */
terom@61: static int pt_png_decode_direct (struct pt_png_img *img, const struct pt_png_header *header, const struct pt_image_params *params, uint8_t *out)
terom@56: {
terom@56:     // write out raw image data a row at a time
terom@56:     for (size_t row = 0; row < header->height; row++) {
terom@56:         // read row data, non-interlaced
terom@56:         png_read_row(img->png, out + row * header->row_bytes, NULL);
terom@56:     }
terom@56: 
terom@56:     return 0;
terom@56: }
terom@56: 
terom@56: /**
terom@56:  * Decode the PNG data, filtering it for sparse regions
terom@56:  */
terom@56: static int pt_png_decode_sparse (struct pt_png_img *img, const struct pt_png_header *header, const struct pt_image_params *params, uint8_t *out)
terom@56: {
terom@56:     // one row of pixel data
terom@56:     uint8_t *row_buf;
terom@56: 
terom@56:     // alloc
terom@56:     if ((row_buf = malloc(header->row_bytes)) == NULL)
terom@56:         RETURN_ERROR(PT_ERR_MEM);
terom@56: 
terom@56:     // decode each row at a time
terom@56:     for (size_t row = 0; row < header->height; row++) {
terom@56:         // read row data, non-interlaced
terom@56:         png_read_row(img->png, row_buf, NULL);
terom@56:         
terom@56:         // skip background-colored regions to keep the cache file sparse
terom@56:         // ...in blocks of PT_CACHE_BLOCK_SIZE bytes
terom@56:         for (size_t col_base = 0; col_base < header->width; col_base += PT_IMG_BLOCK_SIZE) {
terom@56:             // size of this block in bytes
terom@56:             size_t block_size = min(PT_IMG_BLOCK_SIZE * header->col_bytes, header->row_bytes - col_base);
terom@56: 
terom@56:             // ...each pixel
terom@56:             for (
terom@56:                     size_t col = col_base;
terom@56: 
terom@56:                     // BLOCK_SIZE * col_bytes wide, don't go over the edge
terom@56:                     col < col_base + block_size; 
terom@56: 
terom@56:                     col += header->col_bytes
terom@56:             ) {
terom@56:                 // test this pixel
terom@56:                 if (bcmp(row_buf + col, params->background_color, header->col_bytes)) {
terom@56:                     // differs
terom@56:                     memcpy(
terom@56:                             out + row * header->row_bytes + col_base, 
terom@56:                             row_buf + col_base,
terom@56:                             block_size
terom@56:                     );
terom@56:                     
terom@56:                     // skip to next block
terom@56:                     break;
terom@56:                 }
terom@56:             }
terom@56: 
terom@56:             // skip this block
terom@56:             continue;
terom@56:         }
terom@56:     }
terom@56: 
terom@56:     return 0;
terom@56: }
terom@56: 
terom@56: int pt_png_decode (struct pt_png_img *img, const struct pt_png_header *header, const struct pt_image_params *params, uint8_t *out)
terom@56: {
terom@56:     int err;
terom@56: 
terom@61:     // decode
terom@108:     // XXX: it's an array, you silly
terom@61:     if (params->background_color)
terom@61:         err = pt_png_decode_sparse(img, header, params, out);
terom@61: 
terom@61:     else
terom@61:         err = pt_png_decode_direct(img, header, params, out);
terom@61:     
terom@61:     if (err)
terom@56:         return err;
terom@56:     
terom@56:     // finish off, ignore trailing data
terom@56:     png_read_end(img->png, NULL);
terom@56: 
terom@56:     return 0;
terom@56: }
terom@56: 
terom@56: int pt_png_info (struct pt_png_header *header, struct pt_image_info *info)
terom@56: {
terom@56:     // fill in info from header
terom@56:     info->img_width = header->width;
terom@56:     info->img_height = header->height;
terom@56:     info->img_bpp = header->bit_depth;
terom@56: 
terom@56:     return 0;
terom@56: }
terom@56: 
terom@56: /** 
terom@56:  * libpng I/O callback: write out data
terom@56:  */
terom@56: static void pt_png_mem_write (png_structp png, png_bytep data, png_size_t length)
terom@56: {
terom@56:     struct pt_tile_mem *buf = png_get_io_ptr(png);
terom@56:     int err;
terom@56:     
terom@56:     // write to buffer
terom@56:     if ((err = pt_tile_mem_write(buf, data, length)))
terom@69:         // drop err, because png_error doesn't do formatted output
terom@56:         png_error(png, "pt_tile_mem_write: ...");
terom@56: }
terom@56: 
terom@56: /** 
terom@56:  * libpng I/O callback: flush buffered data
terom@56:  */
terom@56: static void pt_png_mem_flush (png_structp png_ptr)
terom@56: {
terom@56:     // no-op
terom@56: }
terom@56: 
terom@56: 
terom@56: /**
terom@56:  * Return a pointer to the pixel data on \a row, starting at \a col.
terom@56:  */
terom@70: static inline const void* tile_row_col (const struct pt_png_header *header, const uint8_t *data, size_t row, size_t col)
terom@56: {
terom@56:     return data + (row * header->row_bytes) + (col * header->col_bytes);
terom@56: }
terom@56: 
terom@56: /**
terom@56:  * Write raw tile image data, directly from the cache
terom@56:  */
terom@70: static int pt_png_encode_direct (struct pt_png_img *img, const struct pt_png_header *header, const uint8_t *data, const struct pt_tile_info *ti)
terom@56: {
terom@56:     for (size_t row = ti->y; row < ti->y + ti->height; row++)
terom@56:         // write data directly
terom@70:         // missing const...
terom@70:         png_write_row(img->png, (const png_bytep) tile_row_col(header, data, row, ti->x));
terom@56: 
terom@56:     return 0;
terom@56: }
terom@56: 
terom@56: /**
terom@100:  * Fill in a clipped region of \a width_px pixels at the given row segment
terom@100:  */
terom@100: static inline void tile_row_fill_clip (const struct pt_png_header *header, png_byte *row, size_t width_px)
terom@100: {
terom@100:     // XXX: use a configureable background color, or full transparency?
terom@100:     memset(row, /* 0xd7 */ 0x00, width_px * header->col_bytes);
terom@100: }
terom@100: 
terom@100: /**
terom@56:  * Write clipped tile image data (a tile that goes over the edge of the actual image) by aligning the data from the cache as needed
terom@56:  */
terom@70: static int pt_png_encode_clipped (struct pt_png_img *img, const struct pt_png_header *header, const uint8_t *data, const struct pt_tile_info *ti)
terom@56: {
terom@56:     png_byte *rowbuf;
terom@56:     size_t row;
terom@56:     
terom@56:     // image data goes from (ti->x ... clip_x, ti->y ... clip_y), remaining region is filled
terom@56:     size_t clip_x, clip_y;
terom@56: 
terom@56: 
terom@69:     // fit the left/bottom edge against the image dimensions
terom@69:     clip_x = min(ti->x + ti->width, header->width);
terom@69:     clip_y = min(ti->y + ti->height, header->height);
terom@56: 
terom@56: 
terom@56:     // allocate buffer for a single row of image data
terom@56:     if ((rowbuf = malloc(ti->width * header->col_bytes)) == NULL)
terom@56:         RETURN_ERROR(PT_ERR_MEM);
terom@56: 
terom@56:     // how much data we actually have for each row, in px and bytes
terom@56:     // from [(tile x)---](clip x)
terom@56:     size_t row_px = clip_x - ti->x;
terom@56:     size_t row_bytes = row_px * header->col_bytes;
terom@56: 
terom@56:     // write the rows that we have
terom@56:     // from [(tile y]---](clip y)
terom@56:     for (row = ti->y; row < clip_y; row++) {
terom@56:         // copy in the actual tile data...
terom@56:         memcpy(rowbuf, tile_row_col(header, data, row, ti->x), row_bytes);
terom@56: 
terom@56:         // generate the data for the remaining, clipped, columns
terom@56:         tile_row_fill_clip(header, rowbuf + row_bytes, (ti->width - row_px));
terom@56: 
terom@56:         // write
terom@56:         png_write_row(img->png, rowbuf);
terom@56:     }
terom@56: 
terom@56:     // generate the data for the remaining, clipped, rows
terom@56:     tile_row_fill_clip(header, rowbuf, ti->width);
terom@56:     
terom@56:     // write out the remaining rows as clipped data
terom@56:     for (; row < ti->y + ti->height; row++)
terom@56:         png_write_row(img->png, rowbuf);
terom@56: 
terom@56:     // ok
terom@56:     return 0;
terom@56: }
terom@56: 
terom@56: /**
terom@56:  * Write unscaled tile data
terom@56:  */
terom@70: static int pt_png_encode_unzoomed (struct pt_png_img *img, const struct pt_png_header *header, const uint8_t *data, const struct pt_tile_info *ti)
terom@56: {
terom@56:     int err;
terom@56: 
terom@56:     // set basic info
terom@56:     png_set_IHDR(img->png, img->info, ti->width, ti->height, header->bit_depth, header->color_type,
terom@56:             PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT
terom@56:     );
terom@56: 
terom@56:     // set palette?
terom@56:     if (header->color_type == PNG_COLOR_TYPE_PALETTE)
terom@61:         // oops... missing const
terom@61:         png_set_PLTE(img->png, img->info, (png_colorp) header->palette, header->num_palette);
terom@56: 
terom@56:     // write meta-info
terom@56:     png_write_info(img->png, img->info);
terom@56: 
terom@56:     // our pixel data is packed into 1 pixel per byte (8bpp or 16bpp)
terom@56:     png_set_packing(img->png);
terom@56:     
terom@56:     // figure out if the tile clips
terom@56:     if (ti->x + ti->width <= header->width && ti->y + ti->height <= header->height)
terom@56:         // doesn't clip, just use the raw data
terom@56:         err = pt_png_encode_direct(img, header, data, ti);
terom@56: 
terom@56:     else
terom@56:         // fill in clipped regions
terom@56:         err = pt_png_encode_clipped(img, header, data, ti);
terom@56:     
terom@56:     return err;
terom@56: }
terom@56: 
terom@56: /**
terom@100:  * Manipulate powers of two
terom@100:  */
terom@100: static inline size_t scale_by_zoom_factor (size_t value, int z)
terom@100: {
terom@100:     if (z > 0)
terom@100:         return value << z;
terom@100: 
terom@100:     else if (z < 0)
terom@100:         return value >> -z;
terom@100: 
terom@100:     else
terom@100:         return value;
terom@100: }
terom@100: 
terom@100: #define ADD_AVG(l, r) (l) = ((l) + (r)) / 2
terom@100: 
terom@100: /**
terom@100:  * Converts a pixel's data into a png_color
terom@100:  */
terom@108: static inline void png_pixel_data (const png_color **outp, const struct pt_png_header *header, const uint8_t *data, size_t row, size_t col)
terom@100: {
terom@100:     if (header->color_type == PNG_COLOR_TYPE_PALETTE) {
terom@100:         // palette entry number
terom@100:         int p;
terom@100: 
terom@100:         if (header->bit_depth == 8)
terom@100:             p = *((uint8_t *) tile_row_col(header, data, row, col));
terom@100:         else
terom@100:             // unknown
terom@100:             return;
terom@100: 
terom@110:         // hrhr - assume our working data is valid (or we have 255 palette entries, so it doesn't matter...)
terom@110:         assert(p < header->num_palette);
terom@100:         
terom@100:         // reference data from palette
terom@108:         *outp = &header->palette[p];
terom@100: 
terom@100:     } else {
terom@100:         // unknown
terom@100:     }
terom@100: }
terom@100: 
terom@100: /**
terom@56:  * Write scaled tile data
terom@56:  */
terom@70: static int pt_png_encode_zoomed (struct pt_png_img *img, const struct pt_png_header *header, const uint8_t *data, const struct pt_tile_info *ti)
terom@56: {
terom@56:     // size of the image data in px
terom@56:     size_t data_width = scale_by_zoom_factor(ti->width, -ti->zoom);
terom@56:     size_t data_height = scale_by_zoom_factor(ti->height, -ti->zoom);
terom@56: 
terom@56:     // input pixels per output pixel
terom@56:     size_t pixel_size = scale_by_zoom_factor(1, -ti->zoom);
terom@56: 
terom@56:     // bytes per output pixel
terom@56:     size_t pixel_bytes = 3;
terom@56: 
terom@56:     // size of the output tile in px
terom@56:     size_t row_width = ti->width;
terom@56: 
terom@56:     // size of an output row in bytes (RGB)
terom@56:     size_t row_bytes = row_width * 3;
terom@56: 
terom@56:     // buffer to hold output rows
terom@56:     uint8_t *row_buf;
terom@100:                 
terom@108:     // color entry for pixel
terom@108:     const png_color *c = &header->palette[0];
terom@56:     
terom@69:     // only supports zooming out...
terom@56:     if (ti->zoom >= 0)
terom@86:         RETURN_ERROR(PT_ERR_TILE_ZOOM);
terom@56: 
terom@56:     if ((row_buf = malloc(row_bytes)) == NULL)
terom@56:         RETURN_ERROR(PT_ERR_MEM);
terom@56: 
terom@56:     // suppress warning...
terom@56:     (void) data_height;
terom@56: 
terom@56:     // define pixel format: 8bpp RGB
terom@56:     png_set_IHDR(img->png, img->info, ti->width, ti->height, 8, PNG_COLOR_TYPE_RGB,
terom@56:             PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT
terom@56:     );
terom@56:     
terom@56:     // write meta-info
terom@56:     png_write_info(img->png, img->info);
terom@56: 
terom@56:     // ...each output row
terom@56:     for (size_t out_row = 0; out_row < ti->height; out_row++) {
terom@56:         memset(row_buf, 0, row_bytes);
terom@56: 
terom@56:         // ...includes pixels starting from this row.
terom@56:         size_t in_row_offset = ti->y + scale_by_zoom_factor(out_row, -ti->zoom);
terom@56:         
terom@56:         // ...each out row includes pixel_size in rows
terom@56:         for (size_t in_row = in_row_offset; in_row < in_row_offset + pixel_size && in_row < header->height; in_row++) {
terom@56:             // and includes each input pixel
terom@56:             for (size_t in_col = ti->x; in_col < ti->x + data_width && in_col < header->width; in_col++) {
terom@56: 
terom@56:                 // ...for this output pixel
terom@56:                 size_t out_col = scale_by_zoom_factor(in_col - ti->x, ti->zoom);
terom@56:                 
terom@56:                 // get pixel RGB data
terom@100:                 png_pixel_data(&c, header, data, in_row, in_col);
terom@56:                 
terom@56:                 // average the RGB data        
terom@108:                 ADD_AVG(row_buf[out_col * pixel_bytes + 0], c->red);
terom@108:                 ADD_AVG(row_buf[out_col * pixel_bytes + 1], c->green);
terom@108:                 ADD_AVG(row_buf[out_col * pixel_bytes + 2], c->blue);
terom@56:             }
terom@56:         }
terom@56: 
terom@56:         // output
terom@56:         png_write_row(img->png, row_buf);
terom@56:     }
terom@56: 
terom@56:     // done
terom@56:     return 0;
terom@56: }
terom@56: 
terom@70: int pt_png_tile (const struct pt_png_header *header, const uint8_t *data, struct pt_tile *tile)
terom@56: {
terom@56:     struct pt_png_img _img, *img = &_img;
terom@56:     struct pt_tile_info *ti = &tile->info;
terom@56:     int err;
terom@56: 
terom@69:     // init img
terom@84:     memset(img, 0, sizeof(*img));
terom@69: 
terom@56:     // check within bounds
terom@56:     if (ti->x >= header->width || ti->y >= header->height)
terom@56:         // completely outside
terom@56:         RETURN_ERROR(PT_ERR_TILE_CLIP);
terom@56:     
terom@56:     // open PNG writer
terom@56:     if ((img->png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL)) == NULL)
terom@56:         JUMP_SET_ERROR(err, PT_ERR_PNG_CREATE);
terom@56:     
terom@56:     if ((img->info = png_create_info_struct(img->png)) == NULL)
terom@56:         JUMP_SET_ERROR(err, PT_ERR_PNG_CREATE);
terom@56: 
terom@56:     // libpng error trap
terom@56:     if (setjmp(png_jmpbuf(img->png)))
terom@56:         JUMP_SET_ERROR(err, PT_ERR_PNG);
terom@56:  
terom@56: 
terom@56: 
terom@56:     // setup output I/O
terom@56:     switch (tile->out_type) {
terom@56:         case PT_TILE_OUT_FILE:
terom@56:             // use default FILE* operation
terom@69:             // do NOT store in img->fh
terom@56:             png_init_io(img->png, tile->out.file);
terom@56: 
terom@56:             break;
terom@56: 
terom@56:         case PT_TILE_OUT_MEM:
terom@56:             // use pt_tile_mem struct via pt_png_mem_* callbacks
terom@56:             png_set_write_fn(img->png, &tile->out.mem, pt_png_mem_write, pt_png_mem_flush);
terom@56: 
terom@56:             break;
terom@56: 
terom@56:         default:
terom@56:             FATAL("tile->out_type: %d", tile->out_type);
terom@56:     }
terom@56: 
terom@56: 
terom@56:   
terom@56:     // unscaled or scaled?
terom@56:     if (ti->zoom)
terom@56:         err = pt_png_encode_zoomed(img, header, data, ti);
terom@56: 
terom@56:     else
terom@56:         err = pt_png_encode_unzoomed(img, header, data, ti);
terom@56: 
terom@56:     if (err)
terom@56:         goto error;
terom@56:     
terom@56: 
terom@56:     // flush remaining output
terom@56:     png_write_flush(img->png);
terom@56: 
terom@56:     // done
terom@56:     png_write_end(img->png, img->info);
terom@56: 
terom@56: error:
terom@56:     // cleanup
terom@56:     pt_png_release_write(img);
terom@56: 
terom@56:     return err;
terom@56: }
terom@56: 
terom@56: 
terom@56: void pt_png_release_read (struct pt_png_img *img)
terom@56: {
terom@56:     png_destroy_read_struct(&img->png, &img->info, NULL);
terom@69:     
terom@69:     // close possible filehandle
terom@69:     if (img->fh) {
terom@69:         if (fclose(img->fh))
terom@69:             log_warn_errno("fclose");
terom@69:     }
terom@56: }
terom@56: 
terom@56: void pt_png_release_write (struct pt_png_img *img)
terom@56: {
terom@56:     png_destroy_write_struct(&img->png, &img->info);
terom@69: 
terom@69:     // close possible filehandle
terom@69:     if (img->fh) {
terom@69:         if (fclose(img->fh))
terom@69:             log_warn_errno("fclose");
terom@69:     }
terom@69: 
terom@56: }
terom@56: