From 8e0bcf40db1076d5ea4eaa90dd776fc5aa9f17e6 Mon Sep 17 00:00:00 2001 From: tarsin Date: Wed, 18 Jan 2023 10:46:21 +0800 Subject: [PATCH] Rewrite the GIF frame delay if it's below a threshold, reland, Resolve #641 --- app/src/main/cpp/gifutils.c | 36 ++++++++++++++++++++++++++++++++---- 1 file changed, 32 insertions(+), 4 deletions(-) diff --git a/app/src/main/cpp/gifutils.c b/app/src/main/cpp/gifutils.c index e8ef2a660..0c56e0837 100644 --- a/app/src/main/cpp/gifutils.c +++ b/app/src/main/cpp/gifutils.c @@ -1,15 +1,43 @@ #include - +#include +#include #include #define LOG_TAG "gifUtils" #include "ehviewer.h" +#define GIF_HEADER_87A "GIF87a" +#define GIF_HEADER_89A "GIF89a" + +static int FRAME_DELAY_START_MARKER = 0x0021F904; + +typedef signed char byte; + +#define FRAME_DELAY_START_MARKER ((byte*)(&FRAME_DELAY_START_MARKER)) +#define MINIMUM_FRAME_DELAY 2 +#define DEFAULT_FRAME_DELAY 10 + +static inline bool isGif(void *addr) { + return !memcmp(addr, GIF_HEADER_87A, 6) || !memcmp(addr, GIF_HEADER_89A, 6); +} + JNIEXPORT void JNICALL Java_com_hippo_image_Image_rewriteGifSource(JNIEnv *env, jclass clazz, jobject buffer) { - void *addr = (*env)->GetDirectBufferAddress(env, buffer); + byte *addr = (*env)->GetDirectBufferAddress(env, buffer); size_t size = (*env)->GetDirectBufferCapacity(env, buffer); - EH_UNUSED(addr); - EH_UNUSED(size); + if (size < 7 || !isGif(addr)) return; + for (size_t i = 0; i < size - 8; i++) { + if (addr[i] == FRAME_DELAY_START_MARKER[3] && addr[i + 1] == FRAME_DELAY_START_MARKER[2] && + addr[i + 2] == FRAME_DELAY_START_MARKER[1] && + addr[i + 3] == FRAME_DELAY_START_MARKER[0]) { + byte *end = addr + i + 4; + if (end[4] != 0) continue; + int frameDelay = end[2] << 8 | end[1]; + if (frameDelay > MINIMUM_FRAME_DELAY) + break; // Quit if the first block looks normal, for performance + end[1] = DEFAULT_FRAME_DELAY; + end[2] = 0; + } + } }