Actually although 2.79 doesn't have *this* issue, it is clearly not reducing the texture limit, which is why this works.

It's not great that we cant access the size of a loaded texture without freeing the previously loaded textures.
AFAICS supporting this would mean larger changes to the image API.

Looked into storing the original size of the GPUTexture before it's clamped.

Here are two patches that do this, I'm thinking the first one is probably better since:

• It doesn't store more data in DNA.
• It doesn't risk values becoming out-of-sync.

• P1006 T65812 possible fix (store original size in the GPUTexture)

  1	diff --git a/source/blender/draw/modes/object_mode.c b/source/blender/draw/modes/object_mode.c
  2	index e8c600ee545..1fb56f2f072 100644
  3	--- a/source/blender/draw/modes/object_mode.c
  4	+++ b/source/blender/draw/modes/object_mode.c
  5	@@ -979,8 +979,8 @@ static void DRW_shgroup_empty_image(OBJECT_Shaders *sh_data,
  6	if (ima != NULL) {
  7	tex = GPU_texture_from_blender(ima, ob->iuser, GL_TEXTURE_2D);
  8	if (tex) {
  9	- size[0] = GPU_texture_width(tex);
  10	- size[1] = GPU_texture_height(tex);
  11	+ size[0] = GPU_texture_orig_width(tex);
  12	+ size[1] = GPU_texture_orig_height(tex);
  13	}
  14	}
  15
  16	diff --git a/source/blender/gpu/GPU_texture.h b/source/blender/gpu/GPU_texture.h
  17	index 3fb7dfc6331..c798788724f 100644
  18	--- a/source/blender/gpu/GPU_texture.h
  19	+++ b/source/blender/gpu/GPU_texture.h
  20	@@ -237,6 +237,9 @@ int GPU_texture_detach_framebuffer(GPUTexture *tex, struct GPUFrameBuffer *fb);
  21	int GPU_texture_target(const GPUTexture *tex);
  22	int GPU_texture_width(const GPUTexture *tex);
  23	int GPU_texture_height(const GPUTexture *tex);
  24	+int GPU_texture_orig_width(const GPUTexture *tex);
  25	+int GPU_texture_orig_height(const GPUTexture *tex);
  26	+void GPU_texture_orig_size_set(GPUTexture *tex, int w, int h);
  27	int GPU_texture_layers(const GPUTexture *tex);
  28	eGPUTextureFormat GPU_texture_format(const GPUTexture *tex);
  29	int GPU_texture_samples(const GPUTexture *tex);
  30	diff --git a/source/blender/gpu/intern/gpu_draw.c b/source/blender/gpu/intern/gpu_draw.c
  31	index 7813ae68371..e48f14a6894 100644
  32	--- a/source/blender/gpu/intern/gpu_draw.c
  33	+++ b/source/blender/gpu/intern/gpu_draw.c
  34	@@ -469,6 +469,9 @@ GPUTexture *GPU_texture_from_blender(Image *ima, ImageUser *iuser, int textarget
  35	BKE_image_release_ibuf(ima, ibuf, NULL);
  36
  37	*tex = GPU_texture_from_bindcode(textarget, bindcode);
  38	+
  39	+ GPU_texture_orig_size_set(*tex, ibuf->x, ibuf->y);
  40	+
  41	return *tex;
  42	}
  43
  44	diff --git a/source/blender/gpu/intern/gpu_texture.c b/source/blender/gpu/intern/gpu_texture.c
  45	index 58d0dd5576f..54e93c361ca 100644
  46	--- a/source/blender/gpu/intern/gpu_texture.c
  47	+++ b/source/blender/gpu/intern/gpu_texture.c
  48	@@ -68,6 +68,7 @@ typedef enum eGPUTextureFormatFlag {
  49	/* GPUTexture */
  50	struct GPUTexture {
  51	int w, h, d; /* width/height/depth */
  52	+ int orig_w, orig_h; /* width/height (of source data), optional. */
  53	int number; /* number for multitexture binding */
  54	int refcount; /* reference count */
  55	GLenum target; /* GL_TEXTURE_* */
  56	@@ -1778,6 +1779,22 @@ int GPU_texture_height(const GPUTexture *tex)
  57	return tex->h;
  58	}
  59
  60	+int GPU_texture_orig_width(const GPUTexture *tex)
  61	+{
  62	+ return tex->orig_w;
  63	+}
  64	+
  65	+int GPU_texture_orig_height(const GPUTexture *tex)
  66	+{
  67	+ return tex->orig_h;
  68	+}
  69	+
  70	+void GPU_texture_orig_size_set(GPUTexture *tex, int w, int h)
  71	+{
  72	+ tex->orig_w = w;
  73	+ tex->orig_h = h;
  74	+}
  75	+
  76	int GPU_texture_layers(const GPUTexture *tex)
  77	{
  78	return tex->d;

• P1007 T65812 possible fix (store original size in the Image ~ DNA)

  1	diff --git a/source/blender/draw/modes/object_mode.c b/source/blender/draw/modes/object_mode.c
  2	index e8c600ee545..1ee23c95d38 100644
  3	--- a/source/blender/draw/modes/object_mode.c
  4	+++ b/source/blender/draw/modes/object_mode.c
  5	@@ -979,8 +979,9 @@ static void DRW_shgroup_empty_image(OBJECT_Shaders *sh_data,
  6	if (ima != NULL) {
  7	tex = GPU_texture_from_blender(ima, ob->iuser, GL_TEXTURE_2D);
  8	if (tex) {
  9	- size[0] = GPU_texture_width(tex);
  10	- size[1] = GPU_texture_height(tex);
  11	+ const int *gpu_size = ima->gputexture_orig_size[TEXTARGET_TEXTURE_2D];
  12	+ size[0] = gpu_size[0];
  13	+ size[1] = gpu_size[1];
  14	}
  15	}
  16
  17	diff --git a/source/blender/gpu/intern/gpu_draw.c b/source/blender/gpu/intern/gpu_draw.c
  18	index 7813ae68371..8a7f9ade969 100644
  19	--- a/source/blender/gpu/intern/gpu_draw.c
  20	+++ b/source/blender/gpu/intern/gpu_draw.c
  21	@@ -196,16 +196,15 @@ float GPU_get_anisotropic(void)
  22
  23	/* Set OpenGL state for an MTFace */
  24
  25	-static GPUTexture **gpu_get_image_gputexture(Image *ima, GLenum textarget)
  26	+static int gpu_get_index_from_textarget(GLenum textarget)
  27	{
  28	if (textarget == GL_TEXTURE_2D) {
  29	- return &ima->gputexture[TEXTARGET_TEXTURE_2D];
  30	+ return TEXTARGET_TEXTURE_2D;
  31	}
  32	else if (textarget == GL_TEXTURE_CUBE_MAP) {
  33	- return &ima->gputexture[TEXTARGET_TEXTURE_CUBE_MAP];
  34	+ return TEXTARGET_TEXTURE_CUBE_MAP;
  35	}
  36	-
  37	- return NULL;
  38	+ return -1;
  39	}
  40
  41	static uint gpu_texture_create_from_ibuf(Image *ima, ImBuf *ibuf, int textarget)
  42	@@ -443,12 +442,23 @@ GPUTexture *GPU_texture_from_blender(Image *ima, ImageUser *iuser, int textarget
  43	ima->gpuflag &= ~IMA_GPU_REFRESH;
  44	}
  45
  46	+ const int tex_index = gpu_get_index_from_textarget(textarget);
  47	+ if (tex_index == -1) {
  48	+ BLI_assert(0);
  49	+ return NULL;
  50	+ }
  51	+
  52	/* Test if we already have a texture. */
  53	- GPUTexture **tex = gpu_get_image_gputexture(ima, textarget);
  54	+ GPUTexture **tex = &(ima->gputexture[tex_index]);
  55	if (*tex) {
  56	return *tex;
  57	}
  58
  59	+ int *gputexture_orig_size = ima->gputexture_orig_size[tex_index];
  60	+
  61	+ gputexture_orig_size[0] = 0;
  62	+ gputexture_orig_size[1] = 0;
  63	+
  64	/* Check if we have a valid image. If not, we return a dummy
  65	* texture with zero bindcode so we don't keep trying. */
  66	uint bindcode = 0;
  67	@@ -469,6 +479,10 @@ GPUTexture *GPU_texture_from_blender(Image *ima, ImageUser *iuser, int textarget
  68	BKE_image_release_ibuf(ima, ibuf, NULL);
  69
  70	*tex = GPU_texture_from_bindcode(textarget, bindcode);
  71	+
  72	+ gputexture_orig_size[0] = ibuf->x;
  73	+ gputexture_orig_size[1] = ibuf->y;
  74	+
  75	return *tex;
  76	}
  77
  78	diff --git a/source/blender/makesdna/DNA_image_types.h b/source/blender/makesdna/DNA_image_types.h
  79	index 5e4ed16d28e..6b4bcec6057 100644
  80	--- a/source/blender/makesdna/DNA_image_types.h
  81	+++ b/source/blender/makesdna/DNA_image_types.h
  82	@@ -112,6 +112,9 @@ typedef struct Image {
  83	/** Not written in file 2 = TEXTARGET_COUNT. */
  84	struct GPUTexture *gputexture[2];
  85
  86	+ /** 2 = TEXTARGET_COUNT. */
  87	+ int gputexture_orig_size[2][2];
  88	+
  89	/* sources from: */
  90	ListBase anims;
  91	struct RenderResult *rr;

First patch seems less intrusive as well +1 for it imho.