sdk: 图片层追加预算解码入口，JPEG 解码期缩解（峰值 43.7→14.0 MiB）
M6 finding（vuln/high）：meow_img_load_file 必先整幅 RGBA 解码，1600×2400 漫画页 瞬时峰值 20.2 MiB（15.4 MiB 输出 + 5.5 MiB YCbCr 平面），超设备 ~14MB 口径， App 侧无法规避。 调研（vendored stb v2.30）：无解码期缩放能力——JPEG 走固定 hs/vs 重采样到全尺寸， PNG 一次性 inflate 整幅 raw_image，公共 API 只有 load/load_16/loadf/info。 完整缩小 IDCT 需改编 1/2、1/4、1/8 IDCT + 进升级系数存储 + MCU 尺寸，改动面大且 易出静默像素错误，故不重写解码器。 改为受控的最小追加（sdk/stb_image.h）： - 新增 stbi_load_scaled / stbi_load_scaled_from_memory：JPEG 输出级按步长 s 抽取 行/列（resample 状态机逐行推进，仅采样行做颜色转换），整幅原尺寸输出缓冲从不 物化；scale<=1 与旧 API 逐字节等价，非 JPEG 忽略。 - 进升级 JPEG：各分量系数 IDCT 进像素平面后立即释放（原来拖到输出分配之后）。 - 旧公共 API 行为不变。 SDK 追加式入口（旧 API 一字未改）： - meow_img_load_file_dim / meow_img_load_mem_dim(path/buf, maxdim)：stbi_info 头探测 选 1/2、1/4、1/8 整数档（取「长边/s ≥ maxdim」最大档，不欠采样），再交既有 meow_img_downscale 精修；小图/maxdim<=0 走旧路径。 - meow_img_probe_file：只读头取尺寸，供 App 在 OOM 前提示。 实测（宿主 test_meow_img_budget，--wrap malloc 打点，全部 PASS）： 8.32MP JPEG 43.70 → 13.96 MiB（新/旧 0.32） 1600×2400 页 20.16 → 9.18 MiB progressive 43.70 → 35.83 MiB（系数阵列扫描期驻留，残余上限） PNG 2400×1600 25.65 → 25.65 MiB（stb 无 PNG 缩解，如实记录） BMP 2400×1600 14.65 → 15.23 MiB（同上，多一次降采样小缓冲） 缩解结果与「整幅解码+downscale」网格平均差 6.28；对 PIL 逐像素比对与全幅解码 同误差量级（mean ≤0.02, max ≤3）。 验证：build_sdk.sh 重编 meow_ui.a 0 warning；examples/hello 重链 0 warning； tuku 用 MEOW_SDK_DIR 指向本分支 sdk 重链 0 warning；既有 test_meow_img_color 仍全 PASS。
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@@ -429,6 +429,14 @@ STBIDEF stbi_uc *stbi_load_from_file (FILE *f, int *x, int *y, int *channels_in
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// for stbi_load_from_file, file pointer is left pointing immediately after image
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#endif
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// 追加（MeowOS SDK M12）：JPEG 解码期降采样。scale>=2 时按 s 抽取输出行/列，
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// 不物化整幅原尺寸输出缓冲（*x,*y 返回 ceil(原尺寸/s)）。scale<=1 与
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// stbi_load / stbi_load_from_memory 完全等价；非 JPEG 格式忽略 scale。
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STBIDEF stbi_uc *stbi_load_scaled_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *channels_in_file, int desired_channels, int scale);
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#ifndef STBI_NO_STDIO
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STBIDEF stbi_uc *stbi_load_scaled (char const *filename, int *x, int *y, int *channels_in_file, int desired_channels, int scale);
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#endif
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#ifndef STBI_NO_GIF
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STBIDEF stbi_uc *stbi_load_gif_from_memory(stbi_uc const *buffer, int len, int **delays, int *x, int *y, int *z, int *comp, int req_comp);
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#endif
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@@ -907,7 +915,7 @@ typedef struct
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#ifndef STBI_NO_JPEG
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static int stbi__jpeg_test(stbi__context *s);
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static void *stbi__jpeg_load(stbi__context *s, int *x, int *y, int *comp, int req_comp, stbi__result_info *ri);
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static void *stbi__jpeg_load_ex(stbi__context *s, int *x, int *y, int *comp, int req_comp, stbi__result_info *ri, int scale);
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static int stbi__jpeg_info(stbi__context *s, int *x, int *y, int *comp);
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#endif
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@@ -1134,7 +1142,7 @@ STBIDEF void stbi_set_flip_vertically_on_load_thread(int flag_true_if_should_fli
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: stbi__vertically_flip_on_load_global)
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#endif // STBI_THREAD_LOCAL
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static void *stbi__load_main(stbi__context *s, int *x, int *y, int *comp, int req_comp, stbi__result_info *ri, int bpc)
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static void *stbi__load_main(stbi__context *s, int *x, int *y, int *comp, int req_comp, stbi__result_info *ri, int bpc, int jpeg_scale)
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{
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memset(ri, 0, sizeof(*ri)); // make sure it's initialized if we add new fields
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ri->bits_per_channel = 8; // default is 8 so most paths don't have to be changed
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@@ -1165,7 +1173,9 @@ static void *stbi__load_main(stbi__context *s, int *x, int *y, int *comp, int re
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// bytes matching expectations; these are prone to false positives, so
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// try them later
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#ifndef STBI_NO_JPEG
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if (stbi__jpeg_test(s)) return stbi__jpeg_load(s,x,y,comp,req_comp, ri);
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if (stbi__jpeg_test(s)) return stbi__jpeg_load_ex(s,x,y,comp,req_comp, ri, jpeg_scale);
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#else
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STBI_NOTUSED(jpeg_scale);
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#endif
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#ifndef STBI_NO_PNM
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if (stbi__pnm_test(s)) return stbi__pnm_load(s,x,y,comp,req_comp, ri);
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@@ -1257,10 +1267,10 @@ static void stbi__vertical_flip_slices(void *image, int w, int h, int z, int byt
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}
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#endif
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static unsigned char *stbi__load_and_postprocess_8bit(stbi__context *s, int *x, int *y, int *comp, int req_comp)
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static unsigned char *stbi__load_and_postprocess_8bit_ex(stbi__context *s, int *x, int *y, int *comp, int req_comp, int jpeg_scale)
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{
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stbi__result_info ri;
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void *result = stbi__load_main(s, x, y, comp, req_comp, &ri, 8);
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void *result = stbi__load_main(s, x, y, comp, req_comp, &ri, 8, jpeg_scale);
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if (result == NULL)
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return NULL;
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@@ -1283,10 +1293,15 @@ static unsigned char *stbi__load_and_postprocess_8bit(stbi__context *s, int *x,
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return (unsigned char *) result;
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}
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static unsigned char *stbi__load_and_postprocess_8bit(stbi__context *s, int *x, int *y, int *comp, int req_comp)
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{
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return stbi__load_and_postprocess_8bit_ex(s, x, y, comp, req_comp, 1);
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}
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static stbi__uint16 *stbi__load_and_postprocess_16bit(stbi__context *s, int *x, int *y, int *comp, int req_comp)
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{
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stbi__result_info ri;
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void *result = stbi__load_main(s, x, y, comp, req_comp, &ri, 16);
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void *result = stbi__load_main(s, x, y, comp, req_comp, &ri, 16, 1);
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if (result == NULL)
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return NULL;
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@@ -1409,6 +1424,19 @@ STBIDEF stbi_us *stbi_load_16(char const *filename, int *x, int *y, int *comp, i
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return result;
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}
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// 追加(M12)：JPEG 解码期降采样（见头文件声明）。非 JPEG 等价于 stbi_load。
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STBIDEF stbi_uc *stbi_load_scaled(char const *filename, int *x, int *y, int *comp, int req_comp, int scale)
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{
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FILE *f = stbi__fopen(filename, "rb");
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stbi_uc *result;
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stbi__context s;
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if (!f) return stbi__errpuc("can't fopen", "Unable to open file");
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stbi__start_file(&s,f);
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result = stbi__load_and_postprocess_8bit_ex(&s,x,y,comp,req_comp, scale);
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if (result) fseek(f, - (int) (s.img_buffer_end - s.img_buffer), SEEK_CUR);
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fclose(f);
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return result;
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}
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#endif //!STBI_NO_STDIO
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@@ -1433,6 +1461,14 @@ STBIDEF stbi_uc *stbi_load_from_memory(stbi_uc const *buffer, int len, int *x, i
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return stbi__load_and_postprocess_8bit(&s,x,y,comp,req_comp);
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}
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// 追加(M12)：JPEG 解码期降采样（见头文件声明）。非 JPEG 等价于 stbi_load_from_memory。
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STBIDEF stbi_uc *stbi_load_scaled_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp, int scale)
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{
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stbi__context s;
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stbi__start_mem(&s,buffer,len);
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return stbi__load_and_postprocess_8bit_ex(&s,x,y,comp,req_comp, scale);
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}
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STBIDEF stbi_uc *stbi_load_from_callbacks(stbi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp)
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{
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stbi__context s;
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@@ -1982,6 +2018,7 @@ typedef struct
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int nomore; // flag if we saw a marker so must stop
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int progressive;
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int scale; // 追加(M12)：输出抽取步长，默认 1=原尺寸
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int spec_start;
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int spec_end;
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int succ_high;
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@@ -3092,6 +3129,12 @@ static void stbi__jpeg_finish(stbi__jpeg *z)
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z->idct_block_kernel(z->img_comp[n].data+z->img_comp[n].w2*j*8+i*8, z->img_comp[n].w2, data);
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}
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}
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// 追加(M12)：该分量系数已全部 IDCT 进像素平面，立即释放，降低进升级 JPEG 的峰值
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if (z->img_comp[n].raw_coeff) {
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STBI_FREE(z->img_comp[n].raw_coeff);
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z->img_comp[n].raw_coeff = 0;
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z->img_comp[n].coeff = 0;
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}
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}
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}
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}
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@@ -3893,6 +3936,10 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
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unsigned int i,j;
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stbi_uc *output;
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stbi_uc *coutput[4] = { NULL, NULL, NULL, NULL };
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stbi_uc *rowbuf = NULL; // 追加(M12)：整行临时缓冲，仅 dec>1 时使用
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int dec = z->scale > 1 ? z->scale : 1;
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int out_w = (z->s->img_x + dec - 1) / dec;
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int out_h = (z->s->img_y + dec - 1) / dec;
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stbi__resample res_comp[4];
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@@ -3918,13 +3965,19 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
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else r->resample = stbi__resample_row_generic;
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}
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// 追加(M12)：dec>1 时整行先转成像素再按步长抽取，不物化整幅原尺寸输出缓冲
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if (dec > 1) {
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rowbuf = (stbi_uc *) stbi__malloc_mad2(n, z->s->img_x, 0);
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if (!rowbuf) { stbi__cleanup_jpeg(z); return stbi__errpuc("outofmem", "Out of memory"); }
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}
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// can't error after this so, this is safe
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output = (stbi_uc *) stbi__malloc_mad3(n, z->s->img_x, z->s->img_y, 1);
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if (!output) { stbi__cleanup_jpeg(z); return stbi__errpuc("outofmem", "Out of memory"); }
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output = (stbi_uc *) stbi__malloc_mad3(n, out_w, out_h, 1);
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if (!output) { STBI_FREE(rowbuf); stbi__cleanup_jpeg(z); return stbi__errpuc("outofmem", "Out of memory"); }
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// now go ahead and resample
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for (j=0; j < z->s->img_y; ++j) {
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stbi_uc *out = output + n * z->s->img_x * j;
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stbi_uc *out;
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for (k=0; k < decode_n; ++k) {
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stbi__resample *r = &res_comp[k];
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int y_bot = r->ystep >= (r->vs >> 1);
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@@ -3939,6 +3992,9 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
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r->line1 += z->img_comp[k].w2;
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}
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}
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// 追加(M12)：resample 状态机须逐行推进（上面已完成）；非采样行直接丢弃
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if (dec > 1 && (j % (unsigned int) dec) != 0) continue;
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out = (dec > 1) ? rowbuf : output + (size_t) n * out_w * j;
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if (n >= 3) {
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stbi_uc *y = coutput[0];
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if (z->s->img_n == 3) {
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@@ -4016,16 +4072,27 @@ static stbi_uc *load_jpeg_image(stbi__jpeg *z, int *out_x, int *out_y, int *comp
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for (i=0; i < z->s->img_x; ++i) { *out++ = y[i]; *out++ = 255; }
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}
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}
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// 追加(M12)：rowbuf 已按整行转好像素，按步长抽取写入输出行
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if (dec > 1) {
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stbi_uc *dst = output + (size_t) n * out_w * (j / (unsigned int) dec);
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unsigned int x;
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for (x=0; x < (unsigned int) out_w; ++x) {
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int c;
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for (c=0; c < n; ++c)
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dst[(size_t) x * n + c] = rowbuf[(size_t) x * dec * n + c];
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}
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}
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}
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STBI_FREE(rowbuf);
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stbi__cleanup_jpeg(z);
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*out_x = z->s->img_x;
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*out_y = z->s->img_y;
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*out_x = out_w;
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*out_y = out_h;
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if (comp) *comp = z->s->img_n >= 3 ? 3 : 1; // report original components, not output
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return output;
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}
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}
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static void *stbi__jpeg_load(stbi__context *s, int *x, int *y, int *comp, int req_comp, stbi__result_info *ri)
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static void *stbi__jpeg_load_ex(stbi__context *s, int *x, int *y, int *comp, int req_comp, stbi__result_info *ri, int scale)
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{
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unsigned char* result;
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stbi__jpeg* j = (stbi__jpeg*) stbi__malloc(sizeof(stbi__jpeg));
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@@ -4033,6 +4100,7 @@ static void *stbi__jpeg_load(stbi__context *s, int *x, int *y, int *comp, int re
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memset(j, 0, sizeof(stbi__jpeg));
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STBI_NOTUSED(ri);
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j->s = s;
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j->scale = scale; // 追加(M12)：输出抽取步长
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stbi__setup_jpeg(j);
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result = load_jpeg_image(j, x,y,comp,req_comp);
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STBI_FREE(j);
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