core:image add support for option .flip_vertical

core/image/bmp/bmp.odin

@@ -242,17 +242,9 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 	case: return img, .Unsupported_Compression
 	}
 
-	// Flipped vertically
-	if info.height < 0 {
-		pixels := mem.slice_data_cast([]RGB_Pixel, img.pixels.buf[:])
-		for y in 0..<img.height / 2 {
-			for x in 0..<img.width {
-				top := y * img.width + x
-				bot := (img.height - y - 1) * img.width + x
-
-				pixels[top], pixels[bot] = pixels[bot], pixels[top]
-			}
-		}
+	// is flipped XOR user wants to flip
+	if (int(info.height < 0) ~ int(.vertical_flip in options)) == 1 {
+		image.vertical_flip(img)
 	}
 	return
 }

core/image/common.odin

@@ -5,13 +5,15 @@
 	List of contributors:
 		Jeroen van Rijn: Initial implementation, optimization.
 		Ginger Bill:     Cosmetic changes.
+		DerTee:          Vertical flip.
 */
 
 // package image implements a general 2D image library to be used with other image related packages
 package image
 
 import "core:bytes"
 import "core:mem"
+import "core:slice"
 import "core:io"
 import "core:compress"
 import "base:runtime"
@@ -133,6 +135,10 @@ Image_Option:
 		color. As this negates the use for an alpha channel, we'll drop it _unless_
 		you also specify `.alpha_add_if_missing`.
 
+	`.vertical_flip`
+		Does an inplace vertical flip of the pixels of the given image on load.
+		This option only supports images with 8 or 16 bit channels!
+
 	Options that don't apply to an image format will be ignored by their loader.
 */
 
@@ -146,6 +152,7 @@ Option :: enum {
 	alpha_drop_if_present,         // Unimplemented for QOI. Returns error.
 	alpha_premultiply,             // Unimplemented for QOI. Returns error.
 	blend_background,              // Ignored for non-PNG formats
+	vertical_flip,                 // Flip image vertically on load
 
 	// Unimplemented
 	do_not_expand_grayscale,
@@ -1438,6 +1445,20 @@ expand_grayscale :: proc(img: ^Image, allocator := context.allocator) -> (ok: bo
 	return true
 }
 
+// Does an inplace vertical flip of the pixels of the given image.
+// Vertical flip is only supported for images with 8 or 16 bit channels!
+vertical_flip :: proc(img: ^Image) {
+	assert(img.depth > 0 && (img.depth % 8  == 0), "Image bit depth must be multiple of 8, currently either 8 or 16 bit!")
+	pixels := img.pixels.buf[:]
+	bytes_per_pixel := img.depth/8 * img.channels
+	stride := img.width * bytes_per_pixel
+	for y in 0..<img.height / 2 {
+		top := y * stride
+		bot := (img.height - y - 1) * stride
+		slice.ptr_swap_non_overlapping(&pixels[top], &pixels[bot], stride)
+	}
+}
+
 /*
 	Helper functions to read and write data from/to a Context, etc.
 */

core/image/netpbm/netpbm.odin

@@ -11,6 +11,7 @@ import "core:unicode"
 import "base:runtime"
 
 Image        :: image.Image
+Options      :: image.Options
 Format       :: image.Netpbm_Format
 Header       :: image.Netpbm_Header
 Info         :: image.Netpbm_Info
@@ -27,7 +28,7 @@ PFM     :: Formats{.Pf, .PF}
 ASCII   :: Formats{.P1, .P2, .P3}
 BINARY  :: Formats{.P4, .P5, .P6} + PAM + PFM
 
-load_from_bytes :: proc(data: []byte, allocator := context.allocator) -> (img: ^Image, err: Error) {
+load_from_bytes :: proc(data: []byte, options := Options{}, allocator := context.allocator) -> (img: ^Image, err: Error) {
 	context.allocator = allocator
 
 	img = new(Image)
@@ -47,6 +48,9 @@ load_from_bytes :: proc(data: []byte, allocator := context.allocator) -> (img: ^
 	}
 	img.metadata = info
 
+	if .vertical_flip in options {
+		image.vertical_flip(img)
+	}
 	return img, nil
 }
 
@@ -722,7 +726,7 @@ autoselect_pbm_format_from_image :: proc(img: ^Image, prefer_binary := true, for
 @(init, private)
 _register :: proc() {
 	loader :: proc(data: []byte, options: image.Options, allocator: mem.Allocator) -> (img: ^Image, err: Error) {
-		return load_from_bytes(data, allocator)
+		return load_from_bytes(data, options, allocator)
 	}
 	destroyer :: proc(img: ^Image) {
 		_ = destroy(img)

core/image/png/png.odin

@@ -1182,6 +1182,9 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 		panic("We should never see bit depths other than 8, 16 and 'Paletted' here.")
 	}
 
+	if .vertical_flip in options {
+		image.vertical_flip(img)
+	}
 	return img, nil
 }
 

core/image/qoi/qoi.odin

@@ -323,6 +323,10 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 		return img, .Post_Processing_Error
 	}
 
+	if .vertical_flip in options {
+		image.vertical_flip(img)
+	}
+
 	return
 }
 

core/image/tga/tga.odin

@@ -304,8 +304,11 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 
 	pixel: RGBA_Pixel
 
+	// is flipped XOR user wants to flip
+	do_read_from_top := bool(int(origin_is_top) ~ int(.vertical_flip in options))
+
 	stride := img.width * dest_channels
-	line   := 0 if origin_is_top else img.height - 1
+	line   := 0 if do_read_from_top else img.height - 1
 
 	for _ in 0..<img.height {
 		offset := line * stride + (0 if origin_is_left else (stride - dest_channels))
@@ -369,7 +372,7 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 			offset += dest_channels if origin_is_left else -dest_channels
 			rle_repetition_count -= 1
 		}
-		line += 1 if origin_is_top else -1
+		line += 1 if do_read_from_top else -1
 	}
 	return img, nil
 }