gif: Split out gif frame data decode.
This commit is contained in:
Michael Drake
Michael Drake
parent
c9a639d2bd
commit
8d8aa0dd46
@ -618,6 +618,83 @@ static gif_result gif__recover_previous_frame(const gif_animation *gif)
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return GIF_OK;
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}
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static inline gif_result
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gif__decode(gif_animation *gif,
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unsigned int frame,
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unsigned int width,
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unsigned int height,
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unsigned int offset_x,
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unsigned int offset_y,
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unsigned int interlace,
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uint8_t minimum_code_size,
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unsigned int *restrict frame_data,
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unsigned int *restrict colour_table)
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{
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const uint8_t *stack_base;
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const uint8_t *stack_pos;
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gif_result ret = GIF_OK;
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lzw_result res;
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/* Initialise the LZW decoding */
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res = lzw_decode_init(gif->lzw_ctx, gif->gif_data,
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gif->buffer_size, gif->buffer_position,
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minimum_code_size, &stack_base, &stack_pos);
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if (res != LZW_OK) {
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return gif_error_from_lzw(res);
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}
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for (unsigned int y = 0; y < height; y++) {
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unsigned int x;
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unsigned int decode_y;
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unsigned int *frame_scanline;
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if (interlace) {
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decode_y = gif_interlaced_line(height, y) + offset_y;
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} else {
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decode_y = y + offset_y;
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}
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frame_scanline = frame_data + offset_x + (decode_y * gif->width);
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/* Rather than decoding pixel by pixel, we try to burst
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* out streams of data to remove the need for end-of
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* data checks every pixel.
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*/
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x = width;
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while (x > 0) {
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unsigned int burst_bytes = (stack_pos - stack_base);
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if (burst_bytes > 0) {
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if (burst_bytes > x) {
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burst_bytes = x;
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}
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x -= burst_bytes;
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while (burst_bytes-- > 0) {
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register unsigned char colour;
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colour = *--stack_pos;
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if (((gif->frames[frame].transparency) &&
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(colour != gif->frames[frame].transparency_index)) ||
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(!gif->frames[frame].transparency)) {
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*frame_scanline = colour_table[colour];
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}
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frame_scanline++;
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}
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} else {
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res = lzw_decode(gif->lzw_ctx, &stack_pos);
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if (res != LZW_OK) {
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/* Unexpected end of frame, try to recover */
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if (res == LZW_OK_EOD) {
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ret = GIF_OK;
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} else {
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ret = gif_error_from_lzw(res);
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}
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break;
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}
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}
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}
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}
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return ret;
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}
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/**
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* decode a gif frame
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*
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@ -638,11 +715,8 @@ gif_internal_decode_frame(gif_animation *gif,
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unsigned int flags, colour_table_size, interlace;
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unsigned int *colour_table;
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unsigned int *frame_data = 0; // Set to 0 for no warnings
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unsigned int *frame_scanline;
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unsigned int save_buffer_position;
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unsigned int return_value = 0;
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unsigned int x, y, decode_y, burst_bytes;
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register unsigned char colour;
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/* Ensure this frame is supposed to be decoded */
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if (gif->frames[frame].display == false) {
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@ -796,10 +870,6 @@ gif_internal_decode_frame(gif_animation *gif,
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/* If we are clearing the image we just clear, if not decode */
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if (!clear_image) {
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lzw_result res;
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const uint8_t *stack_base;
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const uint8_t *stack_pos;
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/* Ensure we have enough data for a 1-byte LZW code size +
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* 1-byte gif trailer
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*/
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@ -863,62 +933,15 @@ gif_internal_decode_frame(gif_animation *gif,
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gif->decoded_frame = frame;
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gif->buffer_position = (gif_data - gif->gif_data) + 1;
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/* Initialise the LZW decoding */
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res = lzw_decode_init(gif->lzw_ctx, gif->gif_data,
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gif->buffer_size, gif->buffer_position,
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gif_data[0], &stack_base, &stack_pos);
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if (res != LZW_OK) {
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return gif_error_from_lzw(res);
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}
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/* Decompress the data */
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for (y = 0; y < height; y++) {
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if (interlace) {
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decode_y = gif_interlaced_line(height, y) + offset_y;
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} else {
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decode_y = y + offset_y;
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}
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frame_scanline = frame_data + offset_x + (decode_y * gif->width);
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/* Rather than decoding pixel by pixel, we try to burst
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* out streams of data to remove the need for end-of
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* data checks every pixel.
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*/
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x = width;
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while (x > 0) {
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burst_bytes = (stack_pos - stack_base);
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if (burst_bytes > 0) {
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if (burst_bytes > x) {
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burst_bytes = x;
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}
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x -= burst_bytes;
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while (burst_bytes-- > 0) {
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colour = *--stack_pos;
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if (((gif->frames[frame].transparency) &&
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(colour != gif->frames[frame].transparency_index)) ||
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(!gif->frames[frame].transparency)) {
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*frame_scanline = colour_table[colour];
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}
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frame_scanline++;
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}
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} else {
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res = lzw_decode(gif->lzw_ctx, &stack_pos);
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if (res != LZW_OK) {
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/* Unexpected end of frame, try to recover */
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if (res == LZW_OK_EOD) {
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return_value = GIF_OK;
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} else {
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return_value = gif_error_from_lzw(res);
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}
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goto gif_decode_frame_exit;
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}
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}
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}
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}
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return_value = gif__decode(gif, frame, width, height,
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offset_x, offset_y, interlace, gif_data[0],
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frame_data, colour_table);
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} else {
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/* Clear our frame */
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if (gif->frames[frame].disposal_method == GIF_FRAME_CLEAR) {
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unsigned int y;
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for (y = 0; y < height; y++) {
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unsigned int *frame_scanline;
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frame_scanline = frame_data + offset_x + ((offset_y + y) * gif->width);
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if (gif->frames[frame].transparency) {
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memset(frame_scanline,
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